Acylated piperidine derivatives as melanocortin-4 receptor agonists

ABSTRACT

Certain novel  4 -substituted N-acylated piperidine derivatives are agonists of the human melanocortin receptor(s) and, in particular, are selective agonists of the human melanocortin- 4  receptor (MC- 4 R). They are therefore useful for the treatment, control, or prevention of diseases and disorders responsive to the activation of MC- 4 R, such as obesity, diabetes, sexual dysfunction, including erectile dysfunction and female sexual dysfunction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C.§371 of PCT Application Ser. No. PCT/US02/05623, filed Feb. 25, 2002,which claims priority under 35 U.S.C. §119 from U.S. ProvisionalApplication Nos. 60/300,572, filed Jun. 22, 2001, and 60/272,258, filedFeb. 28, 2001.

FIELD OF THE INVENTION

The present invention relates to acylated piperidine derivatives, theirsynthesis, and their use as melanocortin receptor (MC-R) agonists. Moreparticularly, the compounds of the present invention are selectiveagonists of the melanocortin-4 receptor (MC-4R) and are thereby usefulfor the treatment of disorders responsive to the activation of MC-4R,such as obesity, diabetes, male sexual dysfunction, and female sexualdysfunction.

BACKGROUND OF THE INVENTION

Pro-opiomelanocortin (POMC) derived peptides are known to affect foodintake. Several lines of evidence support the notion that the G-proteincoupled receptors (GPCRs) of the melanocortin receptor (MC-R) family,several of which are expressed in the brain, are the targets of POMCderived peptides involved in the control of food intake and metabolism.A specific single MC-R that may be targeted for the control of obesityhas not yet been identified, although evidence has been presented thatMC-4R signalling is important in mediating feed behavior (S. Q. Giraudoet al., “Feeding effects of hypothalamic injection of melanocortin-4receptor ligands,” Brain Research, 80: 302–306 (1998)).

Evidence for the involvement of MC-R's in obesity includes: i) theagouti (A^(vy)) mouse which ectopically expresses an antagonist of theMC-1R, MC-3R and -4R is obese, indicating that blocking the action ofthese three MC-R's can lead to hyperphagia and metabolic disorders; ii)MC-4R knockout mice (D. Huszar et al., Cell, 88: 131–141 (1997))recapitulate the phenotype of the agouti mouse and these mice are obese;iii) the cyclic heptapeptide MT-II (a non-selective MC-1R, -3R, -4R, and-5R agonist) injected intracerebroventricularly (ICV) in rodents,reduces food intake in several animal feeding models (NPY, ob/ob,agouti, fasted) while ICV injected SHU-9119 (MC-3R and 4R antagonist;MC-1R and -5R agonist) reverses this effect and can induce hyperphagia;iv) chronic intraperitoneal treatment of Zucker fatty rats with anα-NDP-MSH derivative (HP228) has been reported to activate MC-1R, -3R,-4R, and -5R and to attenuate food intake and body weight gain over a12-week period (I. Corcos et al., “HP228 is a potent agonist ofmelanocortin receptor-4 and significantly attenuates obesity anddiabetes in Zucker fatty rats,” Society for Neuroscience Abstracts, 23:673 (1997)).

Five distinct MC-R's have thus far been identified, and these areexpressed in different tissues. MC-1R was initially characterized bydominant gain of function mutations at the Extension locus, affectingcoat color by controlling phaeomelanin to eumelanin conversion throughcontrol of tyrosinase. MC-1R is mainly expressed in melanocytes. MC-2Ris expressed in the adrenal gland and represents the ACTH receptor.MC-3R is expressed in the brain, gut, and placenta and may be involvedin the control of food intake and thermogenesis. MC-4R is uniquelyexpressed in the brain, and its inactivation was shown to cause obesity(A. Kask, et al., “Selective antagonist for the melanocortin-4 receptor(HS014) increases food intake in free-feeding rats,” Biochem. Biophys.Res. Commun., 245: 90–93 (1998)). MC-5R is expressed in many tissues,including white fat, placenta and exocrine glands. A low level ofexpression is also observed in the brain. MC-5R knockout mice revealreduced sebaceous gland lipid production (Chen et al., Cell, 91: 789–798(1997)).

Erectile dysfunction denotes the medical condition of inability toachieve penile erection sufficient for successful sexual intercourse.The term “impotence” is oftentimes employed to describe this prevalentcondition. Approximately 140 million men worldwide, and, according to aNational Institutes of Health study, about 30 million American mensuffer from impotency or erectile dysfunction. It has been estimatedthat the latter number could rise to 47 million men by the year 2000.Erectile dysfunction can arise from either organic or psychogeniccauses, with about 20% of such cases being purely psychogenic in origin.Erectile dysfunction increases from 40% at age 40, to 67% at age 75,with over 75% occurring in men over the age of 50. In spite of thefrequent occurrence of this condition, only a small number of patientshave received treatment because existing treatment alternatives, such asinjection therapies, penile prosthesis implantation, and vacuum pumps,have been uniformly disagreeable [for a discussion, see “ABC of sexualhealth—erectile dysfunction,” Brit. Med. J. 318: 387–390 (1999)]. Onlymore recently have more viable treatment modalities become available, inparticular orally active agents, such as sildenafil citrate, marketed byPfizer under the brand name of Viagra®. (See “Emerging pharmacologicaltherapies for erectile dysfunction,” Exp. Opin. Ther. Patents 9:1689–1696 (1999)). Sildenafil is a selective inhibitor of type Vphosphodiesterase (PDE-V), a cyclic-GMP-specific phosphodiesteraseisozyme [see R. B. Moreland et al., “Sildenafil: A Novel Inhibitor ofPhosphodiesterase Type 5 in Human Corpus Cavernosum Smooth MuscleCells,” Life Sci., 62: 309–318 (1998)]. Prior to the introduction ofViagra on the market, less than 10% of patients suffering from erectiledysfunction received treatment. Sildenafil is also being evaluated inthe clinic for the treatment of female sexual dysfunction.

The regulatory approval of Viagra® for the oral treatment of erectiledysfunction has invigorated efforts to discover even more effectivemethods to treat erectile dysfunction. Several additional selectivePDE-V inhibitors are in clinical trials. UK-114542 is a sildenafilbackup from Pfizer with supposedly improved properties. Tadalafil orIC-351 (ICOS Corp.) is claimed to have greater selectivity for PDE-Vover PDE-VI than sildenafil. Other PDE-V inhibitors include vardenafilfrom Bayer, M-54033 and M-54018 from Mochida Pharmaceutical Co., andE-4010 from Eisai Co., Ltd.

Other pharmacological approaches to the treatment of erectiledysfunction have been described [see, e.g., “Latest Findings on theDiagnosis and Treatment of Erectile Dysfunction,” Drug News &Perspectives, 9: 572–575 (1996); “Oral Pharmacotherapy in ErectileDysfunction,” Current Opinion in Urology, 7: 349–353 (1997)]. A productunder clinical development by Zonagen is an oral formulation of thealpha-adrenoceptor antagonist phentolamine mesylate under the brand nameof Vasomax®. Vasomax® is also being evaluated for the treatment offemale sexual dysfunction.

Drugs to treat erectile dysfunction act either peripherally orcentrally. They are also classified according to whether they “initiate”a sexual response or “facilitate” a sexual response to prior stimulation[for a discussion, see “A Therapeutic Taxonomy of Treatments forErectile Dysfunction: An Evolutionary Imperative,” Int. J. ImpotenceRes., 9: 115–121 (1997)]. While sildenafil and phentolamine actperipherally and are considered to be “enhancers” or “facilitators” ofthe sexual response to erotic stimulation, sildenafil appears to beefficacious in both mild organic and psychogenic erectile dysfunction.Sildenafil has an onset of action of 30–60 minutes after an oral dosewith the effect lasting about 4 hours, whereas phentolamine requires5–30 minutes for onset with a duration of 2 hours. Although sildenafilis effective in a majority of patients, it takes a relatively long timefor the compound to show the desired effects. The faster-actingphentolamine appears to be less effective and to have a shorter durationof action than sildenafil. Oral sildenafil is effective in about 70% ofmen who take it, whereas an adequate response with phentolamine isobserved in only 35–40% of patients. Both compounds require eroticstimulation for efficacy. Since sildenafil indirectly increases bloodflow in the systemic circulation by enhancing the smooth musclerelaxation effects of nitric oxide, it is contraindicated for patientswith unstable heart conditions or cardiovascular disease, in particularpatients taking nitrates, such as nitroglycerin, to treat angina. Otheradverse effects associated with the clinical use of sildenafil includeheadache, flushing, dyspepsia, and “abnormal vision,” the latter theresult of inhibition of the type VI phosphodiesterase isozyme (PDE-VI),a cyclic-GMP-specific phosphodiesterase that is concentrated in theretina. “Abnormal vision” is defined as a mild and transient “bluish”tinge to vision, but also an increased sensitivity to light or blurredvision.

Synthetic melanocortin receptor agonists (melanotropic peptides) havebeen found to initiate erections in men with psychogenic erectiledysfunction [See H. Wessells et al., “Synthetic Melanotropic PeptideInitiates Erections in Men With Psychogenic Erectile Dysfunction:Double-Blind, Placebo Controlled Crossover Study,” J. Urol., 160:389–393 (1998); Fifteenth American Peptide Symposium, Jun. 14–19, 1997(Nashville Tenn.)]. Activation of melanocortin receptors of the brainappears to cause normal stimulation of sexual arousal. In the abovestudy, the centrally acting α-melanocyte-stimulating hormone analog,melanotan-II (MT-II), exhibited a 75% response rate, similar to resultsobtained with apomorphine, when injected intramuscularly orsubcutaneously to males with psychogenic erectile dysfunction. MT-II isa synthetic cyclic heptapeptide, Ac-Nle-c[Asp-His-DPhe-Arg-Trp-Lys]-NH₂,which contains the 4–10 melanocortin receptor binding region common toα-MSH and adrenocorticotropin, but with a lactam bridge. It is anon-selective MC-1R, -3R, -4R, and -5R agonist (Dorr et al., LifeSciences, Vol. 58, 1777–1784, 1996). MT-II (also referred to as PT-14)(Erectide®) is presently in clinical development by PalatinTechnologies, Inc. and TheraTech, Inc. as a non-penile subcutaneousinjection formulation. It is considered to be an “initiator” of thesexual response. The time to onset of erection with this drug isrelatively short (10–20 minutes) with a duration of action approximately2.5 hours. Adverse reactions observed with MT-II include nausea,flushing, loss of appetite, stretching, and yawning and may be theresult of activation of MC-1R, MC-2R, MC-3R, and/or MC-5R. MT-II must beadministered parenterally, such as by subcutaneous, intravenous, orintramuscular route, since it is not absorbed into the systemiccirculation when given by the oral route.

MT-II's erectogenic properties apparently are not limited to cases ofpsychogenic erectile dysfunction in that men with a variety of organicrisk factors developed penile erections upon subcutaneous injection ofthe compound; moreover, the level of sexual desire was significantlyhigher after MT-II administration than after placebo [see H. Wessells,“Effect of an Alpha-Melanocyte Stimulating Hormone Analog on PenileErection and Sexual Desire in Men with Organic Erectile Dysfunction,”Urology, 56: 641–646 (2000)].

Compositions of melanotropic peptides and methods for the treatment ofpsychogenic erectile dysfunction are disclosed in U.S. Pat. No.5,576,290, assigned to Competitive Technologies. Methods of stimulatingsexual response in females using melanotropic peptides have beendisclosed in U.S. Pat. No. 6,051,555.

Spiropiperidine and piperidine derivatives have been disclosed in WO99/64002 (16 Dec. 1999); WO 00/74679 (14 Dec. 2000); WO 01/70708 (27Sep. 2001); WO 01/70337 (27 Sep. 2001); and WO 01/91752 (6 Dec. 2001) asagonists of the melanocortin receptor(s) and particularly as selectiveagonists of the MC-4R receptor and thereby useful for the treatment ofdiseases and disorders, such as obesity, diabetes, and sexualdysfunction, including erectile dysfunction and female sexualdysfunction.

Because of the unresolved deficiencies of the various pharmacologicalagents discussed above, there is a continuing need in the medical artsfor improved methods and compositions to treat individuals sufferingfrom psychogenic and/or organic sexual dysfunction. Such methods shouldhave wider applicability, enhanced convenience and ease of compliance,short onset of action, reasonably long duration of action, and minimalside effects with few contraindications, as compared to agents nowavailable.

It is therefore an object of the present invention to provide acylatedpiperidine derivatives which are melanocortin receptor agonists andthereby useful to treat obesity, diabetes, male sexual dysfunction, andfemale sexual dysfunction.

It is another object of the present invention to provide acylatedpiperidine derivatives which are selective agonists of themelanocortin-4 (MC-4R) receptor.

It is another object of the present invention to provide pharmaceuticalcompositions comprising the melanocortin receptor agonists of thepresent invention with a pharmaceutically acceptable carrier.

It is another object of the present invention to provide methods for thetreatment or prevention of disorders, diseases, or conditions responsiveto the activation of the melanocortin-4 receptor in a subject in needthereof by administering the compounds and pharmaceutical compositionsof the present invention.

It is another object of the present invention to provide methods for thetreatment or prevention of obesity, diabetes mellitus, male sexualdysfunction, and female sexual dysfunction by administering thecompounds and pharmaceutical compositions of the present invention to asubject in need thereof.

It is another object of the present invention to provide methods for thetreatment of erectile dysfunction by administering the compounds andpharmaceutical compositions of the present invention to a subject inneed thereof.

These and other objects will become readily apparent from the detaileddescription that follows.

SUMMARY OF THE INVENTION

The present invention relates to novel 4-substituted N-acylatedpiperidines of structural formula I:

These acylated piperidine derivatives are effective as melanocortinreceptor agonists and are particularly effective as selectivemelanocortin-4 receptor (MC-4R) agonists. They are therefore useful forthe treatment and/or prevention of disorders responsive to theactivation of MC-4R, such as obesity, diabetes as well as male andfemale sexual dysfunction, in particular, male erectile dysfunction.

The present invention also relates to pharmaceutical compositionscomprising the compounds of the present invention and a pharmaceuticallyacceptable carrier.

The present invention also relates to methods for the treatment orprevention of disorders, diseases, or conditions responsive to theactivation of the melanocortin receptor in a subject in need thereof byadministering the compounds and pharmaceutical compositions of thepresent invention.

The present invention also relates to methods for the treatment orprevention of obesity, diabetes mellitus, male sexual dysfunction, andfemale sexual dysfunction by administering the compounds andpharmaceutical compositions of the present invention.

The present invention also relates to methods for treating erectiledysfunction by administering the compounds and pharmaceuticalcompositions of the present invention.

The present invention also relates to methods for treating erectiledysfunction by administering the compounds of the present invention incombination with a therapeutically effective amount of another agentknown to be useful to treat the condition.

The present invention also relates to methods for treating or preventingobesity by administering the compounds of the present invention incombination with a therapeutically effective amount of another agentknown to be useful to treat or prevent the condition.

The present invention also relates to methods for treating or preventingdiabetes by administering the compounds of the present invention incombination with a therapeutically effective amount of another agentknown to be useful to treat or prevent the condition.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to 4-substituted N-acylated piperidinederivatives useful as melanocortin receptor agonists, in particular, asselective MC-4R agonists. Compounds of the present invention aredescribed by structural formula I:

or a pharmaceutically acceptable salt thereof;wherein

-   r is 1 or 2;-   s is 0, 1, or 2;-   n is 0, 1, or 2;-   p is 0, 1, or 2;-   R¹ is selected from the group consisting of    -   hydrogen,    -   amidino,    -   C₁₋₄ alkyliminoyl,    -   C₁₋₁₀ alkyl,    -   (CH₂)_(n)—C₃₋₇ cycloalkyl,    -   (CH₂)_(n)-phenyl,    -   (CH₂)_(n)-naphthyl, and    -   (CH₂)_(n)-heteroaryl wherein heteroaryl is selected from the        group consisting of        -   (1) pyridinyl,        -   (2) furyl,        -   (3) thienyl,        -   (4) pyrrolyl,        -   (5) oxazolyl,        -   (6) thiazolyl,        -   (7) imidazolyl,        -   (8) pyrazolyl,        -   (9) isoxazolyl,        -   (10) isothiazolyl,        -   (11) pyrimidinyl,        -   (12) pyrazinyl,        -   (13) pyridazinyl,        -   (14) quinolyl,        -   (15) isoquinolyl,        -   (16) benzimidazolyl,        -   (17) benzofuryl,        -   (18) benzothienyl,        -   (19) indolyl,        -   (20) benzthiazolyl, and        -   (21) benzoxazolyl;            in which phenyl, naphthyl, and heteroaryl are unsubstituted            or substituted with one to three groups independently            selected from R³; and alkyl and cycloalkyl are unsubstituted            or substituted with one to three groups independently            selected from R³ and oxo;-   R² is selected from the group consisting of    -   phenyl,    -   naphthyl, and    -   heteroaryl wherein heteroaryl is selected from the group        consisting of        -   (1) pyridinyl,        -   (2) furyl,        -   (3) thienyl,        -   (4) pyrrolyl,        -   (5) oxazolyl,        -   (6) thiazolyl,        -   (7) imidazolyl,        -   (8) pyrazolyl,        -   (9) isoxazolyl,        -   (10) isothiazolyl,        -   (11) pyrimidinyl,        -   (12) pyrazinyl,        -   (13) pyridazinyl,        -   (14) quinolyl,        -   (15) isoquinolyl,        -   (16) benzimidazolyl,        -   (17) benzofuryl,        -   (18) benzothienyl,        -   (19) indolyl,        -   (20) benzthiazolyl, and        -   (21) benzoxazolyl;            in which phenyl, naphthyl, and heteroaryl are unsubstituted            or substituted with one to three groups independently            selected from R³;-   R³ is selected from the group consisting of    -   C₁₋₆ alkyl,    -   (CH₂)_(n)-phenyl,    -   (CH₂)_(n)-naphthyl,    -   (CH₂)_(n)-heteroaryl,    -   (CH₂)_(n)-heterocyclyl,    -   (CH₂)_(n)C₃₋₇ cycloalkyl,    -   halogen,    -   OR⁴,    -   (CH₂)_(n)N(R⁴)₂,    -   (CH₂)_(n)C≡N,    -   CO₂R⁴,    -   C(R⁴)(R⁴)N(R⁴)₂,    -   NO₂,    -   (CH₂)_(n)NR⁴SO₂R⁴    -   (CH₂)_(n)SO₂N(R⁴)₂,    -   (CH₂)_(n)S(O)_(p)R⁴,    -   (CH₂)_(n)NR⁴C(O)N(R⁴)₂,    -   (CH₂)_(n)C(O)N(R⁴)₂,    -   (CH₂)_(n)NR⁴C(O)R⁴,    -   (CH₂)_(n)NR⁴CO₂R⁴,    -   CF₃,    -   CH₂CF₃,    -   OCF₃, and    -   OCH₂CF₃;        in which heteroaryl is as defined above; phenyl, naphthyl,        heteroaryl, cycloalkyl, and heterocyclyl are unsubstituted or        substituted with one to three substituents independently        selected from halogen, hydroxy, C₁₋₄ alkyl, trifluoromethyl, and        C₁₋₄ alkoxy; and (CH₂)_(n) is unsubstituted or substituted with        one to two groups independently selected from halogen, hydroxy,        and C₁₋₄ alkyl;-   each R⁴ is independently selected from the group consisting of    -   hydrogen,    -   C₁₋₆ alkyl,    -   (CH₂)_(n)-phenyl,    -   (CH₂)_(n)-naphthyl, and    -   (CH₂)_(n)C₃₋₇ cycloalkyl;        wherein cycloalkyl is unsubstituted or substituted with one to        three groups independently selected from halogen, C₁₋₄ alkyl,        and C₁₋₄ alkoxy; or two R⁴ groups together with the atom to        which they are attached form a 4- to 8-membered mono- or        bicyclic ring system optionally containing an additional        heteroatom selected from O, S, and NC₁₋₄ alkyl;-   each R⁵ is independently selected from the group consisting of    -   hydrogen,    -   C₁₋₈ alkyl,    -   (CH₂)_(n)-phenyl,    -   (CH₂)_(n)-naphthyl,    -   (CH₂)_(n)-heteroaryl, and    -   (CH₂)_(n)C₃₋₇ cycloalkyl;        wherein heteroaryl is as defined above; phenyl, naphthyl, and        heteroaryl are unsubstituted or substituted with one to three        groups independently selected from R³; and alkyl, cycloalkyl,        and (CH₂)_(n) are unsubstituted or substituted with one to three        groups independently selected from R³ and oxo; or two R⁵ groups        together with the atom to which they are attached form a 5- to        8-membered mono- or bicyclic ring system optionally containing        an additional heteroatom selected from O, S, and NC₁₋₄ alkyl;-   X is selected from the group consisting of    -   C₁₋₈ alkyl,    -   (CH₂)_(n)C₃₋₈ cycloalkyl,    -   (CH₂)_(n)-phenyl,    -   (CH₂)_(n)-naphthyl,    -   (CH₂)_(n)-heteroaryl,    -   (CH₂)_(n)heterocyclyl,    -   (CH₂)_(n)C≡N,    -   (CH₂)_(n)CON(R⁵R⁵),    -   (CH₂)_(n)CO₂R⁵,    -   (CH₂)_(n)COR⁵,    -   (CH₂)_(n)NR⁵C(O)R⁵,    -   (CH₂)_(n)NR⁵CO₂R⁵,    -   (CH₂)_(n)NR⁵C(O)N(R⁵)₂,    -   (CH₂)_(n)NR⁵SO₂R⁵,    -   (CH₂)_(n)S(O)_(p)R⁵,    -   (CH₂)_(n)SO₂N(R⁵)(R⁵),    -   (CH₂)_(n)OR⁵,    -   (CH₂)_(n)OC(O)R⁵,    -   (CH₂)_(n)OC(O)OR⁵,    -   (CH₂)_(n)OC(O)N(R⁵)₂,    -   (CH₂)_(n)N(R⁵)(R⁵), and    -   (CH₂)_(n)NR⁵SO₂N(R⁵)(R⁵);        wherein heteroaryl is as defined above; phenyl, naphthyl, and        heteroaryl are unsubstituted or substituted with one to three        groups independently selected from R³; and alkyl, (CH₂)_(n),        cycloalkyl, and heterocyclyl are unsubstituted or substituted        with one to three groups independently selected from R³ and oxo;-   Y is selected from the group consisting of    -   hydrogen,    -   C₁₋₈ alkyl,    -   C₂₋₆ alkenyl,    -   (CH₂)_(n)C₃₋₈ cycloalkyl,    -   (CH₂)_(n)-phenyl,    -   (CH₂)_(n)-naphthyl,    -   (CH₂)_(n)-heteroaryl, and    -   (CH₂)_(n)-heterocyclyl;        wherein heteroaryl is as defined above, and phenyl, naphthyl,        and heteroaryl are unsubstituted or substituted with one to        three groups independently selected from R³; and alkyl,        (CH₂)_(n), cycloalkyl, and heterocyclyl are optionally        substituted with one to three groups independently selected from        R³ and oxo.

In one embodiment of the compounds of structural formula I, R¹ isselected from the group consisting of hydrogen, C₁₋₆ alkyl, (CH₂)₀₋₁C₃₋₆cycloalkyl, and (CH₂)₀₋₁-phenyl; wherein phenyl is unsubstituted orsubstituted with one to three groups independently selected from R³; andalkyl and cycloalkyl are optionally substituted with one to three groupsindependently selected from R³ and oxo.

In a second embodiment of the compounds of structural formula I, R² isphenyl or thienyl optionally substituted with one to three groupsindependently selected from R³. In a class of this embodiment, R² isphenyl optionally substituted with one to three groups independentlyselected from R³.

In a third embodiment of the compounds of structural formula I, X isselected from the group consisting of C₁₋₆ alkyl, (CH₂)_(n)-phenyl,(CH₂)n-naphthyl, (CH₂)_(n)-heteroaryl, (CH₂)_(n)-heterocyclyl,(CH₂)_(n)C(O)N(R⁵)(R⁵), (CH₂)_(n)CO₂R⁵, (CH₂)_(n)S(O)_(p)R⁵,(CH₂)_(n)OR⁵, (CH₂)_(n)NR⁵C(O)R⁵, and (CH₂)_(n)NR⁵SO₂R⁵; whereinheteroaryl is as defined above, and phenyl, naphthyl, and heteroaryl areoptionally substituted with one to three groups independently selectedfrom R³; alkyl and heterocyclyl are optionally substituted with one tothree groups independently selected from R³ and oxo; and the (CH₂)_(n)group is optionally substituted with one to three groups independentlyselected from R⁴, halogen, S(O)_(p)R⁴, N(R⁴)₂, and OR⁴. In a class ofthis embodiment, X is selected from the group consisting of C₁₋₆ alkyl,(CH₂)₀₋₁-phenyl, (CH₂)₀₋₁-heteroaryl, (CH₂)0-1-heterocyclyl,(CH₂)₀₋₁NHC(O)R⁵, (CH₂)₀₋₁CO₂R⁵, and (CH₂)₀₋₁C(O)N(R⁵)(R⁵); whereinphenyl and heteroaryl are optionally substituted with one to threegroups independently selected from R³; and alkyl and heterocyclyl areoptionally substituted with one to three groups independently selectedfrom R³ and oxo. In a subclass of this class, heteroaryl is selectedfrom the group consisting of pyridyl, pyrazinyl, pyrimidinyl, triazolyl,tetrazolyl, thiadiazolyl, oxadiazolyl, pyrazolyl, and imidazolyl.

In a fourth embodiment of compounds of formula I, Y is selected from thegroup consisting of C₁₋₈ alkyl, C₂₋₆ alkenyl, (CH₂)C₃₋₈ cycloalkyl,(CH₂)-phenyl, (CH₂)-naphthyl, (CH₂)-heterocyclyl, and (CH₂)-heteroaryl,wherein phenyl, naphthyl, and heteroaryl are optionally substituted withone to three groups independently selected from R³; and (CH₂)_(n),alkyl, cycloalkyl, and heterocyclyl are optionally substituted with oneto three groups independently selected from R³ and oxo. In a class ofthis embodiment, Y is selected from the group consisting of C₁₋₈ alkyl,C₂₋₆ alkenyl, C₅₋₇ cycloalkyl, and phenyl; wherein phenyl isunsubstituted or substituted with one to three groups independentlyselected from R³; and alkyl and cycloalkyl are unsubstituted orsubstituted with one to three groups independently selected from R³ andoxo. In a subclass of this class, Y is cyclohexyl or C₁₋₆ alkyl; whereinthe cyclohexyl and alkyl groups are unsubstituted or substituted withone to three groups independently selected from R³ and oxo.

In yet a further embodiment of compounds of structural formula I, r is 1or 2 and s is 1.

In yet a further embodiment of the compounds of the present invention,there are provided compounds of structural formula IIa or IIb of theindicated relative stereochemical configurations having the transorientation of the R² and piperidinecarbonyl substituents:

or a pharmaceutically acceptable salt thereof;wherein

-   r is 1 or 2;-   n is 0, 1, or 2;-   p is 0, 1, or 2;-   R¹ is hydrogen, amidino, C₁₋₄ alkyliminoyl, C₁₋₆ alkyl, C₅₋₆    cycloalkyl, (CH₂)₀₋₁ phenyl, (CH₂)₀₋₁ heteroaryl; wherein phenyl and    heteroaryl are unsubstituted or substituted with one to three groups    independently selected from R³, and alkyl and cycloalkyl are    unsubstituted or substituted with one to three groups independently    selected from R³ and oxo;-   R² is phenyl or thienyl optionally substituted with one to three    groups independently selected from R³;-   R³ is selected from the group consisting of    -   C₁₋₆ alkyl,    -   (CH₂)_(n)-phenyl,    -   (CH₂)_(n)-naphthyl,    -   (CH₂)_(n)-heteroaryl,    -   (CH₂)_(n)-heterocyclyl,    -   (CH₂)_(n)C₃₋₇ cycloalkyl,    -   halogen,    -   OR⁴,    -   (CH₂)_(n)N(R⁴)₂,    -   (CH₂)_(n)C≡N,    -   CO₂R⁴,    -   C(R⁴)(R⁴)N(R⁴)₂,    -   NO₂,    -   (CH₂)_(n)NR⁴SO₂R⁴    -   (CH₂)_(n)SO₂N(R⁴)₂,    -   (CH₂)_(n)S(O)_(p)R⁴,    -   (CH₂)_(n)NR⁴C(O)N(R⁴)₂,    -   (CH₂)_(n)C(O)N(R⁴)₂,    -   (CH₂)_(n)NR⁴C(O)R⁴,    -   (CH₂)_(n)NR⁴CO₂R⁴,    -   CF₃,    -   CH₂CF₃,    -   OCF₃, and    -   OCH₂CF₃;        in which heteroaryl is as defined above; phenyl, naphthyl,        heteroaryl, cycloalkyl, and heterocyclyl are unsubstituted or        substituted with one to two substituents independently selected        from halogen, hydroxy, C₁₋₄ alkyl, trifluoromethyl, and C₁₋₄        alkoxy; and (CH₂)_(n) is unsubstituted or substituted with one        to two groups independently selected from halogen, hydroxy, and        C₁₋₄ alkyl;-   each R⁴ is independently selected from the group consisting of    -   hydrogen,    -   C₁₋₈ alkyl, and    -   C₃₋₆ cycloalkyl;        wherein cycloalkyl is unsubstituted or substituted with one to        three groups independently selected from halogen, C₁₋₄ alkyl,        and C₁₋₄ alkoxy; or two R⁴ groups together with the atom to        which they are attached form a 4- to 8-membered mono- or        bicyclic ring system optionally containing an additional        heteroatom selected from O, S, and NC₁₋₄ alkyl;-   Y is selected from the group consisting of    -   C₁₋₈ alkyl,    -   C₂₋₆ alkenyl,    -   (CH₂)₀₋₁C₃₋₈ cycloalkyl,    -   (CH₂)₀₋₁-phenyl,    -   (CH₂)₀₋₁-naphthyl, and    -   (CH₂)₀₋₁-heteroaryl;        wherein phenyl, naphthyl, and heteroaryl are unsubstituted or        substituted with one to three groups independently selected from        R³; and alkyl, (CH₂), and cycloalkyl are unsubstituted or        substituted with one to three groups independently selected from        R³ and oxo; and-   X is selected from the group consisting of:

In yet a further embodiment of the compounds of the present invention,there are provided compounds of structural formula IIIa or IIIb of theindicated relative stereochemical configurations having the transorientation of the phenyl and piperidinecarbonyl substituents:

or a pharmaceutically acceptable salt thereof;wherein

-   r is 1 or 2;-   R¹ is hydrogen, C₁₋₄ alkyl or (CH₂)₀₋₁ phenyl;-   each R³ is independently selected from the group consisting of    hydrogen, halogen, C₁₋₄ alkyl, trifluoromethyl, and C₁₋₄ alkoxy;-   Y is cyclohexyl or phenyl; and-   X is selected from the group consisting of

Illustrative but nonlimiting examples of compounds of the presentinvention that are useful as melanocortin agonists are the following:

or a pharmaceutically acceptable salt thereof.

The compounds of structural formula I are effective as melanocortinreceptor agonists and are particularly effective as selective agonistsof MC-4R. They are therefore useful for the treatment and/or preventionof disorders responsive to the activation of MC-4R, such as obesity,diabetes as well as male and/or female sexual dysfunction, inparticular, erectile dysfunction, and further in particular, maleerectile dysfunction.

Another aspect of the present invention provides a method for thetreatment or prevention of obesity or diabetes in a subject in needthereof which comprises administering to said subject a therapeuticallyor prophylactically effective amount of a compound of structural formulaI.

Another aspect of the present invention provides a method for thetreatment or prevention of male or female sexual dysfunction includingerectile dysfunction which comprises administering to a subject in needof such treatment or prevention a therapeutically or prophylacticallyeffective amount of a compound of structural formula I.

Another aspect of the present invention provides a pharmaceuticalcomposition comprising a compound of structural formula I and apharmaceutically acceptable carrier.

Yet another aspect of the present invention provides a method for thetreatment or prevention of male or female sexual dysfunction includingerectile dysfunction which comprises administering to a subject in needof such treatment or prevention a therapeutically or prophylacticallyeffective amount of a compound of structural formula I in combinationwith a therapeutically effective amount of another agent known to beuseful for the treatment of these conditions.

Yet another aspect of the present invention provides a method for thetreatment or prevention of obesity which comprises administering to asubject in need of such treatment or prevention a therapeutically orprophylactically effective amount of a compound of structural formula Iin combination with a therapeutically effective amount of another agentknown to be useful for the treatment of this condition.

Throughout the instant application, the following terms have theindicated meanings:

The alkyl groups specified above are intended to include those alkylgroups of the designated length in either a straight or branchedconfiguration. Exemplary of such alkyl groups are methyl, ethyl, propyl,isopropyl, butyl, sec-butyl, tertiary butyl, pentyl, isopentyl, hexyl,isohexyl, and the like.

The term “halogen” is intended to include the halogen atoms fluorine,chlorine, bromine and iodine.

The term “C₁₋₄ alkyliminoyl” means C₁₋₃C(═NH)—.

The term “aryl” includes phenyl and naphthyl.

The term “heteroaryl” includes mono- and bicyclic aromatic ringscontaining from 1 to 4 heteroatoms selected from nitrogen, oxygen andsulfur. “5- or 6-Membered heteroaryl” represents a monocyclicheteroaromatic ring; examples thereof include thiazole, oxazole,thiophene, furan, pyrrole, imidazole, isoxazole, pyrazole, triazole,thiadiazole, tetrazole, oxadiazole, pyridine, pyridazine, pyrimidine,pyrazine, and the like. Bicyclic heteroaromatic rings include, but arenot limited to, benzothiadiazole, indole, benzothiophene, benzofuran,benzimidazole, benzisoxazole, benzothiazole, quinoline, benzotriazole,benzoxazole, isoquinoline, purine, furopyridine and thienopyridine.

The term “5- or 6-membered carbocyclyl” is intended to includenon-aromatic rings containing only carbon atoms such as cyclopentyl andcyclohexyl.

The term “5 and 6-membered heterocyclyl” is intended to includenonaromatic heterocycles containing one to four heteroatoms selectedfrom nitrogen, oxygen and sulfur. Examples of a 5 or 6-memberedheterocyclyl include piperidine, morpholine, thiamorpholine,pyrrolidine, imidazolidine, tetrahydrofuran, piperazine, and the like.

Certain of the above defined terms may occur more than once in the aboveformula and upon such occurrence each term shall be definedindependently of the other; thus for example, NR⁴R⁴ may represent NH₂,NHCH₃, N(CH₃)CH₂CH₃, and the like.

An embodiment of the term “mammal in need thereof” is a “human in needthereof,” said human being either male or female.

The term “composition”, as in pharmaceutical composition, is intended toencompass a product comprising the active ingredient(s), and the inertingredient(s) that make up the carrier, as well as any product whichresults, directly or indirectly, from combination, complexation oraggregation of any two or more of the ingredients, or from dissociationof one or more of the ingredients, or from other types of reactions orinteractions of one or more of the ingredients. Accordingly, thepharmaceutical compositions of the present invention encompass anycomposition made by admixing a compound of the present invention and apharmaceutically acceptable carrier.

“Erectile dysfunction” is a disorder involving the failure of a malemammal to achieve erection, ejaculation, or both. Symptoms of erectiledysfunction include an inability to achieve or maintain an erection,ejaculatory failure, premature ejaculation, or inability to achieve anorgasm. An increase in erectile dysfunction is often associated with ageand is generally caused by a physical disease or as a side-effect ofdrug treatment.

By a melanocortin receptor “agonist” is meant an endogenous or drugsubstance or compound that can interact with a melanocortin receptor andinitiate a pharmacological response characteristic of the melanocortinreceptor. By a melanocortin receptor “antagonist” is meant a drug or acompound that opposes the melanocortin receptor-associated responsesnormally induced by another bioactive agent. The “agonistic” propertiesof the compounds of the present invention were measured in thefunctional assay described below. The functional assay discriminates amelanocortin receptor agonist from a melanocortin receptor antagonist.

By “binding affinity” is meant the ability of a compound/drug to bind toits biological target, in the the present instance, the ability of acompound of structural formula I to bind to a melanocortin receptor.Binding affinities for the compounds of the present invention weremeasured in the binding assay described below and are expressed asIC₅₀'s.

“Efficacy” describes the relative intensity with which agonists vary inthe response they produce even when they occupy the same number ofreceptors and with the same affinity. Efficacy is the property thatenables drugs to produce responses. Properties of compounds/drugs can becategorized into two groups, those which cause them to associate withthe receptors (binding affinity) and those that produce a stimulus(efficacy). The term “efficacy” is used to characterize the level ofmaximal responses induced by agonists. Not all agonists of a receptorare capable of inducing identical levels of maximal responses. Maximalresponse depends on the efficiency of receptor coupling, that is, fromthe cascade of events, which, from the binding of the drug to thereceptor, leads to the desired biological effect.

The functional activities expressed as EC₅₀'s and the “agonist efficacy”for the compounds of the present invention at a particular concentrationwere measured in the functional assay described below.

Optical Isomers—Diastereomers—Geometric Isomers—Tautomers

Compounds of structural formula I contain one or more asymmetric centersand can thus occur as racemates and racemic mixtures, singleenantiomers, diastereomeric mixtures and individual diastereomers. Thepresent invention is meant to comprehend all such isomeric forms of thecompounds of structural formula I.

Some of the compounds described herein contain olefinic double bonds,and unless specified otherwise, are meant to include both E and Zgeometric isomers.

Some of the compounds described herein may exist as tautomers such asketo-enol tautomers. The individual tautomers as well as mixturesthereof are encompassed within the compounds of structural formula I.

Compounds of structural formula I may be separated into their individualdiastereoisomers by, for example, fractional crystallization from asuitable solvent, for example methanol or ethyl acetate or a mixturethereof, or via chiral chromatography using an optically activestationary phase. Absolute stereochemistry may be determined by X-raycrystallography of crystalline products or crystalline intermediateswhich are derivatized, if necessary, with a reagent containing anasymmetric center of known absolute configuration.

Alternatively, any stereoisomer of a compound of the general formula I,IIa, IIb, IIIa, and IIIb may be obtained by stereospecific synthesisusing optically pure starting materials or reagents of known absoluteconfiguration.

Salts

The term “pharmaceutically acceptable salts” refers to salts preparedfrom pharmaceutically acceptable non-toxic bases or acids includinginorganic or organic bases and inorganic or organic acids. Salts derivedfrom inorganic bases include aluminum, ammonium, calcium, copper,ferric, ferrous, lithium, magnesium, manganic salts, manganous,potassium, sodium, zinc, and the like. Particularly preferred are theammonium, calcium, lithium, magnesium, potassium, and sodium salts.Salts derived from pharmaceutically acceptable organic non-toxic basesinclude salts of primary, secondary, and tertiary amines, substitutedamines including naturally occurring substituted amines, cyclic amines,and basic ion exchange resins, such as arginine, betaine, caffeine,choline, N,N′-dibenzylethylenediamine, diethylamine,2-diethylaminoethanol, 2-dimethylaminoethanol, ethanolamine,ethylenediamine, N-ethyl-morpholine, N-ethylpiperidine, glucamine,glucosamine, histidine, hydrabamine, isopropylamine, lysine,methylglucamine, morpholine, piperazine, piperidine, polyamine resins,procaine, purines, theobromine, triethylamine, trimethylamine,tripropylamine, tromethamine, and the like.

When the compound of the present invention is basic, salts may beprepared from pharmaceutically acceptable non-toxic acids, includinginorganic and organic acids. Such acids include acetic, benzenesulfonic,benzoic, camphorsulfonic, citric, ethanesulfonic, formic, fumaric,gluconic, glutamic, hydrobromic, hydrochloric, isethionic, lactic,maleic, malic, mandelic, methanesulfonic, malonic, mucic, nitric,pamoic, pantothenic, phosphoric, propionic, succinic, sulfuric,tartaric, p-toluenesulfonic acid, trifluoroacetic acid, and the like.Particularly preferred are citric, fumaric, hydrobromic, hydrochloric,maleic, phosphoric, sulfuric, and tartaric acids.

It will be understood that, as used herein, references to the compoundsof Formula I are meant to also include the pharmaceutically acceptablesalts.

Utility

Compounds of formula I are melanocortin receptor agonists and as suchare useful in the treatment, control or prevention of diseases,disorders or conditions responsive to the activation of one or more ofthe melanocortin receptors including, but are not limited to, MC-1,MC-2, MC-3, MC-4, or MC-5. Such diseases, disorders or conditionsinclude, but are not limited to, obesity (by reducing appetite,increasing metabolic rate, reducing fat intake or reducing carbohydratecraving), diabetes mellitus (by enhancing glucose tolerance, decreasinginsulin resistance), hypertension, hyperlipidemia, osteoarthritis,cancer, gall bladder disease, sleep apnea, depression, anxiety,compulsion, neuroses, insomnia/sleep disorder, substance abuse, pain,male and female sexual dysfunction (including impotence, loss of libidoand erectile dysfunction), fever, inflammation, immunemodulation,rheumatoid arthritis, skin tanning, acne and other skin disorders,neuroprotective and cognitive and memory enhancement including thetreatment of Alzheimer's disease. Some compounds encompassed by formulaI show highly selective affinity for the melanocortin-4 receptorrelative to MC-1R, MC-2R, MC-3R, and MC-5R, which makes them especiallyuseful in the prevention and treatment of obesity, as well as maleand/or female sexual dysfunction, including erectile dysfunction.

“Male sexual dysfunction” includes impotence, loss of libido, anderectile dysfunction.

“Erectile dysfunction” is a disorder involving the failure of a malemammal to achieve erection, ejaculation, or both. Symptoms of erectiledysfunction include an inability to achieve or maintain an erection,ejaculatory failure, premature ejaculation, or inability to achieve anorgasm. An increase in erectile dysfunction and sexual dysfunction canhave numerous underlying causes, including but not limited to (1) aging,(b) an underlying physical dysfunction, such as trauma, surgery, andperipheral vascular disease, and (3) side-effects resulting from drugtreatment, depression, and other CNS disorders.

“Female sexual dysfunction” can be seen as resulting from multiplecomponents including dysfunction in desire, sexual arousal, sexualreceptivity, and orgasm related to disturbances in the clitoris, vagina,periurethral glans, and other trigger points of sexual function. Inparticular, anatomic and functional modification of such trigger pointsmay diminish the orgasmic potential in breast cancer and gynecologiccancer patients. Treatment of female sexual dysfunction with an MC-4receptor agonist can result in improved blood flow, improvedlubrication, improved sensation, facilitation of reaching orgasm,reduction in the refractory period between orgasms, and improvements inarousal and desire. In a broader sense, “female sexual dysfunction” alsoincorporates sexual pain, premature labor, and dysmenorrhea.

Administration and Dose Ranges

Any suitable route of administration may be employed for providing amammal, especially a human with an effective dosage of a compound of thepresent invention. For example, oral, rectal, topical, parenteral,ocular, pulmonary, nasal, and the like may be employed. Dosage formsinclude tablets, troches, dispersions, suspensions, solutions, capsules,creams, ointments, aerosols, and the like. Preferably compounds ofFormula I are administered orally or topically.

The effective dosage of active ingredient employed may vary depending onthe particular compound employed, the mode of administration, thecondition being treated and the severity of the condition being treated.Such dosage may be ascertained readily by a person skilled in the art.

When treating obesity, in conjunction with diabetes and/orhyperglycemia, or alone, generally satisfactory results are obtainedwhen the compounds of the present invention are administered at a dailydosage of from about 0.001 milligram to about 100 milligrams perkilogram of animal body weight, preferably given in a single dose or individed doses two to six times a day, or in sustained release form. Inthe case of a 70 kg adult human, the total daily dose will generally befrom about 0.07 milligrams to about 3500 milligrams. This dosage regimenmay be adjusted to provide the optimal therapeutic response.

When treating diabetes mellitus and/or hyperglycemia, as well as otherdiseases or disorders for which compounds of formula I are useful,generally satisfactory results are obtained when the compounds of thepresent invention are administered at a daily dosage of from about 0.001milligram to about 100 milligram per kilogram of animal body weight,preferably given in a single dose or in divided doses two to six times aday, or in sustained release form. In the case of a 70 kg adult human,the total daily dose will generally be from about 0.07 milligrams toabout 350 milligrams. This dosage regimen may be adjusted to provide theoptimal therapeutic response.

For the treatment of sexual dysfunction compounds of the presentinvention are given in a dose range of 0.001 milligram to about 100milligram per kilogram of body weight, preferably as a single doseorally or as a nasal spray.

Combination Therapy

Compounds of Formula I may be used in combination with other drugs thatare used in the treatment/prevention/suppression or amelioration of thediseases or conditions for which compounds of Formula I are useful. Suchother drugs may be administered, by a route and in an amount commonlyused therefor, contemporaneously or sequentially with a compound ofFormula I. When a compound of Formula I is used contemporaneously withone or more other drugs, a pharmaceutical composition containing suchother drugs in addition to the compound of Formula I is preferred.Accordingly, the pharmaceutical compositions of the present inventioninclude those that also contain one or more other active ingredients, inaddition to a compound of Formula I.

Examples of other active ingredients that may be combined with acompound of Formula I for the treatment or prevention of obesity and/ordiabetes, either administered separately or in the same pharmaceuticalcompositions, include, but are not limited to:

(a) insulin sensitizers including (i) PPARγ agonists such as theglitazones (e.g. troglitazone, pioglitazone, englitazone, MCC-555,BRL49653 and the like), and compounds disclosed in WO97/27857, 97/28115,97/28137 and 97/27847; (ii) biguanides such as metformin and phenformin;

(b) insulin or insulin mimetics;

(c) sulfonylureas, such as tolbutamide and glipizide;

(d) α-glucosidase inhibitors (such as acarbose),

(e) cholesterol lowering agents such as (i) HMG-CoA reductase inhibitors(lovastatin, simvastatin, pravastatin, fluvastatin, atorvastatin, andother statins), (ii) sequestrants (cholestyramine, colestipol and adialkylaminoalkyl derivatives of a cross-linked dextran), (ii) nicotinylalcohol nicotinic acid or a salt thereof, (iii) proliferator-activaterreceptor α agonists such as fenofibric acid derivatives (gemfibrozil,clofibrate, fenofibrate and benzafibrate), (iv) inhibitors ofcholesterol absorption for example beta-sitosterol and (acylCoA:cholesterol acyltransferase) inhibitors for example melinamide, (v)probucol, (vi) vitamin E, and (vii) thyromimetics;

(f) PPARδ agonists, such as those disclosed in WO97/28149;

(g) anti-obesity serotonergic agents, such as fenfluramine,dexfenfluramine, phentermine, and sibutramine;

(h) β3-adrenoreceptor agonists;

(i) pancreatic lipase inhibitors, such as orlistat;

(j) feeding behavior modifying agents, such as neuropeptide Y Y1 and Y5antagonists, such as those disclosed in WO 97/19682, WO 97/20820, WO97/20821, WO 97/20822, WO 97/20823, WO 01/14376, and U.S. Pat. No.6,191,160;

(k) orexin-1 receptor antagonists;

(l) PPARα agonists such as described in WO 97/36579 by Glaxo;

(m) PPARγ antagonists as described in WO 97/10813;

(n) serotonin reuptake inhibitors such as fluoxetine, paroxetine, andsertraline;

(o) growth hormone secretagogues, such as MK-0677;

(p) cannabinoid receptor ligands, such as cannabinoid CB₁ receptorantagonists or inverse agonists; and

(q) protein tyrosine phosphatase-1B (PTP-1B) inhibitors.

Examples of anti-obesity agents that can be employed in combination witha compound of Formula I are disclosed in “Patent focus on newanti-obesity agents,” Exp. Opin. Ther. Patents, 10: 819–831 (2000);“Novel anti-obesity drugs,” Exp. Opin. Invest. Drugs, 9: 1317–1326(2000); and “Recent advances in feeding suppressing agents: potentialtherapeutic strategy for the treatment of obesity, Exp. Pin. Ther.Patents, 11: 1677–1692 (2001). The role of neuropeptide Y in obesity isdiscussed in Exp. Opin. Invest. Drugs, 9: 1327–1346 (2000). Cannabinoidreceptor ligands are discussed in Exp. Opin. Invest. Drugs, 9: 1553–1571(2000).

Examples of other active ingredients that may be combined with acompound of Formula I for the treatment or prevention of male or femalesexual dysfunction, in particular, male erectile dysfunction, eitheradministered separately or in the same pharmaceutical compositions,include, but are not limited to (a) type V cyclic-GMP-specificphosphodiesterase (PDE-V) inhibitors, including sildenafil and (6R,12aR)-2,3,6,7,12,12a-hexahydro-2-methyl-6-(3,4-methylenedioxyphenyl)-pyrazino[2′,1′:6,1]pyrido[3,4-b]indole-1,4-dione(IC-351); (b) alpha-adrenergic receptor antagonists, includingphentolamine and yohimbine or pharmaceutically acceptable salts thereof;(c) dopamine receptor agonists, such as apomorphine or pharmaceuticallyacceptable salts thereof; and (d) nitric oxide (NO) donors.

Pharmaceutical Compositions

Another aspect of the present invention provides pharmaceuticalcompositions which comprises a compound of Formula I and apharmaceutically acceptable carrier. The pharmaceutical compositions ofthe present invention comprise a compound of Formula I as an activeingredient or a pharmaceutically acceptable salt thereof, and may alsocontain a pharmaceutically acceptable carrier and optionally othertherapeutic ingredients. The term “pharmaceutically acceptable salts”refers to salts prepared from pharmaceutically acceptable non-toxicbases or acids including inorganic bases or acids and organic bases oracids.

The compositions include compositions suitable for oral, rectal,topical, parenteral (including subcutaneous, intramuscular, andintravenous), ocular (ophthalmic), pulmonary (nasal or buccalinhalation), or nasal administration, although the most suitable routein any given case will depend on the nature and severity of theconditions being treated and on the nature of the active ingredient.They may be conveniently presented in unit dosage form and prepared byany of the methods well-known in the art of pharmacy.

In practical use, the compounds of Formula I can be combined as theactive ingredient in intimate admixture with a pharmaceutical carrieraccording to conventional pharmaceutical compounding techniques. Thecarrier may take a wide variety of forms depending on the form ofpreparation desired for administration, e.g., oral or parenteral(including intravenous). In preparing the compositions for oral dosageform, any of the usual pharmaceutical media may be employed, such as,for example, water, glycols, oils, alcohols, flavoring agents,preservatives, coloring agents and the like in the case of oral liquidpreparations, such as, for example, suspensions, elixirs and solutions;or carriers such as starches, sugars, microcrystalline cellulose,diluents, granulating agents, lubricants, binders, disintegrating agentsand the like in the case of oral solid preparations such as, forexample, powders, hard and soft capsules and tablets, with the solidoral preparations being preferred over the liquid preparations.

Because of their ease of administration, tablets and capsules representthe most advantageous oral dosage unit form in which case solidpharmaceutical carriers are obviously employed. If desired, tablets maybe coated by standard aqueous or nonaqueous techniques. Suchcompositions and preparations should contain at least 0.1 percent ofactive compound. The percentage of active compound in these compositionsmay, of course, be varied and may conveniently be between about 2percent to about 60 percent of the weight of the unit. The amount ofactive compound in such therapeutically useful compositions is such thatan effective dosage will be obtained. The active compounds can also beadministered intranasally as, for example, liquid drops or spray.

The tablets, pills, capsules, and the like may also contain a bindersuch as gum tragacanth, acacia, corn starch or gelatin; excipients suchas dicalcium phosphate; a disintegrating agent such as corn starch,potato starch, alginic acid; a lubricant such as magnesium stearate; anda sweetening agent such as sucrose, lactose or saccharin. When a dosageunit form is a capsule, it may contain, in addition to materials of theabove type, a liquid carrier such as a fatty oil.

Various other materials may be present as coatings or to modify thephysical form of the dosage unit. For instance, tablets may be coatedwith shellac, sugar or both. A syrup or elixir may contain, in additionto the active ingredient, sucrose as a sweetening agent, methyl andpropylparabens as preservatives, a dye and a flavoring such as cherry ororange flavor.

Compounds of formula I may also be administered parenterally. Solutionsor suspensions of these active compounds can be prepared in watersuitably mixed with a surfactant such as hydroxy-propylcellulose.Dispersions can also be prepared in glycerol, liquid polyethyleneglycols and mixtures thereof in oils. Under ordinary conditions ofstorage and use, these preparations contain a preservative to preventthe growth of microorganisms.

The pharmaceutical forms suitable for injectable use include sterileaqueous solutions or dispersions and sterile powders for theextemporaneous preparation of sterile injectable solutions ordispersions. In all cases, the form must be sterile and must be fluid tothe extent that easy syringability exists. It must be stable under theconditions of manufacture and storage and must be preserved against thecontaminating action of microorganisms such as bacteria and fungi. Thecarrier can be a solvent or dispersion medium containing, for example,water, ethanol, polyol (e.g. glycerol, propylene glycol and liquidpolyethylene glycol), suitable mixtures thereof, and vegetable oils.

Preparation of Compounds of the Invention

The compounds of structural formula I of the present invention can beprepared according to the procedures of the following Schemes andExamples, using appropriate materials and are further exemplified by thefollowing specific examples. Moreover, by utilizing the proceduresdescribed in detail in PCT International Application Publications WO99/64002 (16 Dec. 1999) and WO 00/74679 (14 Dec. 2000), which areincorporated by reference herein in their entirety, in conjunction withthe disclosure contained herein, one of ordinary skill in the art canreadily prepare additional compounds of the present invention claimedherein. The compounds illustrated in the examples are not, however, tobe construed as forming the only genus that is considered as theinvention. The Examples further illustrate details for the preparationof the compounds of the present invention. Those skilled in the art willreadily understand that known variations of the conditions and processesof the following preparative procedures can be used to prepare thesecompounds. The instant compounds are generally isolated in the form oftheir pharmaceutically acceptable salts, such as those describedpreviously hereinabove. The free amine bases corresponding to theisolated salts can be generated by neutralization with a suitable base,such as aqueous sodium hydrogencarbonate, sodium carbonate, sodiumhydroxide, and potassium hydroxide, and extraction of the liberatedamine free base into an organic solvent followed by evaporation. Theamine free base isolated in this manner can be further converted intoanother pharmaceutically acceptable salt by dissolution in an organicsolvent followed by addition of the appropriate acid and subsequentevaporation, precipitation, or crystallization. All temperatures aredegrees Celsius unless otherwise noted. Mass spectra (MS) were measuredby electron-spray ion-mass spectroscopy.

The phrase “standard peptide coupling reaction conditions” meanscoupling a carboxylic acid with an amine using an acid activating agentsuch as EDC, DCC, and BOP in an inert solvent such as methylene chloridein the presence of a catalyst such as HOBT. The use of protecting groupsfor the amine and carboxylic acid functionalities to facilitate thedesired reaction and minimize undesired reactions is well documented.Conditions required to remove protecting groups are found in standardtextbooks such as Greene, T, and Wuts, P. G. M., Protective Groups inOrganic Synthesis, John Wiley & Sons, Inc., New York, N.Y., 1991. CBZand BOC are commonly used protecting groups in organic synthesis, andtheir removal conditions are known to those skilled in the art. Forexample, CBZ may be removed by catalytic hydrogenation in the presenceof a noble metal or its oxide such as palladium on activated carbon in aprotic solvent such as methanol or ethanol. In cases where catalytichydrogenation is contraindicated due to the presence of otherpotentially reactive functionalities, removal of CBZ groups can also beachieved by treatment with a solution of hydrogen bromide in acetic acidor by treatment with a mixture of TFA and dimethylsulfide. Removal ofBOC protecting groups is carried out with a strong acid, such astrifluoroacetic acid, hydrochloric acid, or hydrogen chloride gas, in asolvent such as methylene chloride, methanol, or ethyl acetate.

Abbreviations Used in the Description of the Preparation of theCompounds of the Present Invention: BOC (boc) t-butyloxycarbonyl BOPbenzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluorophosphateBu butyl calc. calculated CBZ (Cbz) benzyloxycarbonyl c-hex cyclohexylc-pen cyclopentyl c-pro cyclopropyl DEAD diethyl azodicarboxylate DIEAdiisopropylethylamine DMAP 4-dimethylaminopyridine DMFN,N-dimethylformamide EDC 1-(3-dimethylaminopropyl)3-ethylcarbodiimideHCl eq. equivalent(s) ES-MS electron spray ion-mass spectroscopy Etethyl EtOAc ethyl acetate HATUN-[(dimethylamino)-1H-1,2,3-triazolo[4,5-b] pyridin-1-ylmethylene]-N-methylmethanaminium hexafluorophosphate N-oxide HOAt1-hydroxy-7-azabenzotriazole HOBt 1-hydroxybenzotriazole hydrate HPLChigh performance liquid chromatography LDA lithium diisopropylamideMC-xR melanocortin receptor (x being a number) Me methyl MF molecularformula MS mass spectrum Ms methanesulfonyl OTf trifluoromethanesulfonylPh phenyl Phe phenylalanine Pr propyl prep. prepared PyBropbromo-tris-pyrrolidino-phosphonium hexafluorophosphate r.t. roomtemperature TFA trifluoroacetic acid THF tetrahydrofuran TLC thin-layerchromatography.

Reaction Schemes A-L illustrate the methods employed in the synthesis ofthe compounds of the present invention of structural formula I. Allsubstituents are as defined above unless indicated otherwise.

Reaction Scheme A illustrates a key step in the synthesis of the novelcompounds of structural formula I of the present invention. As shown inreaction Scheme A, the reaction of a 4-substituted piperidine of 1 witha carboxylic acid derivative of formula 2 affords a title compound ofstructural formula I where R¹ is an N-tert-butoxycarbonyl group (N-BOC).The amide bond coupling reaction illustrated in reaction Scheme A isconducted in an appropriate inert solvent such as methylene chloride,dimethylformamide (DMF) or the like and may be performed with a varietyof reagents suitable for amide coupling reactions such as1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) orbenzotriazol-1-yloxytripyrrolidinephosphonium hexafluorophosphate(PyBOP). Preferred conditions for the amide bond coupling reaction shownin reaction Scheme A are known to those skilled in organic synthesis.Such modifications may include, but are not limited to, the use of basicreagents such as triethylamine (TEA) or N-methylmorpholine (NMM), or theaddition of an additive such as 1-hydroxybenzotriazole (HOBt).Alternatively, 4-substituted piperidines of formula 1 may be treatedwith an active ester or acid chloride derived from carboxylic acid 2which also affords compounds of structural formula I (R¹=BOC). The amidebond coupling shown in reaction Scheme A is usually conducted attemperatures between 0° C. and room temperature, occasionally atelevated temperatures, and the coupling reaction is typically conductedfor periods of 1 to 24 hours.

If it is desired to produce a compound of structural formula I whereinR¹ is a hydrogen, the N-BOC protected compounds of structural formula Iare then deprotected under acidic conditions, for instance usingtrifluoroacetic acid in a solvent like methylene chloride at roomtemperature.

When it is desired to prepare compounds of structural formula I whereinR¹ is not a hydrogen, the compounds of general formula I (R¹=H) may befurther modified using the methodology described below in reactionScheme L.

Reaction Schemes B-I illustrate methods for the synthesis of thecarboxylic acids of general formula 2 that are utilized in the amidebond coupling reaction shown in reaction Scheme A. Reaction Schemes J-Killustrate additional methods for the synthesis of 4-substitutedpiperidines of general formula 1 that are used in that same step. Thecompounds of structural formula 1 in which the R¹ substituent is a groupother than a hydrogen atom are generally prepared from compounds ofstructural formula I wherein R=H using a variety of synthetic methodsknown in the literature of organic synthesis. Specific examples of suchtransformations are outlined in reaction Schemes and provided in theprocedures for the Examples presented below.

Reaction Scheme B illustrates a preferred method for the synthesis ofcompounds of general formula 2 wherein r is 2 and s is 1 such that theresulting heterocycle is a 3-aryl-4-piperidine carboxylic acidderivative 10. The synthesis of 10 begins with a commercially availableβ-keto ester such as 3. Generally a protecting group interchange of anN-BOC group for the N-benzyl group is performed initially. Thus a β-ketoester of formula 3 is subjected to debenzylation by hydrogenolysis usinga palladium-on-carbon catalyst in a solvent system such as 1:1ethanol-water under a hydrogen atmosphere. The resulting piperidone 4 isthen protected as its tert-butyl carbamate using BOC anhydride in thepresence of a base and a suitable solvent. For example, this can beaccomplished in a two phase mixture of chloroform and aqueous sodiumbicarbonate as shown. Incorporation of the 3-aryl substituent is thenperformed in two steps. First, the β-keto ester group is converted tothe corresponding vinyl triflate 6 using trifluoromethanesulfonicanhydride and an organic base like N,N-diisopropylethylamine in anaprotic solvent such as methylene chloride. The resulting vinyl triflate6 is then subjected to a palladium-catalyzed cross-coupling reactionwith an aryl boronic acid (7) using a palladium (II) catalyst such as[1,1′-bis(diphenylphosphino)-ferrocene]dichloropalladium(II). Preferredconditions for this reaction are the use of a toluene-ethanol-aqueoussodium carbonate solvent system at an elevated temperature, for instance50–100° C., for a period of 2–24 hours. The resulting aryl-substitutedtetrahydropyridine derivative 8 can be reduced to a piperidine such as 9using a variety of known techniques and the method chosen will determinethe stereochemical outcome of the product. For instance, hydrogenationof 8 with a palladium on carbon catalyst in a solvent such as ethanolaffords cis-3,4-disubstituted piperidines of general formula 9.Alternatively, a dissolving metal reduction using a metal, such asmagnesium in methanol, reduces the double bond of 8 and produces amixture of both cis and trans 3,4-disubstituted piperidines of formula9. The resulting mixture of cis and trans diastereoisomers may beseparated chromatographically or it may be subsequently epimerized toafford the pure trans isomer of 9 by treating the mixture with a baselike sodium methoxide in methanol. Finally, hydrolysis of either the cisor trans 3-aryl-4-piperidine carboxylic ester 9 affords either a cis ortrans 3-aryl-4-piperidine carboxylic acid of general formula 10,corresponding to an acid of general formula 2 wherein r is 2 and s is 1.The cis or trans carboxylic acids of general formula 10 are produced asracemates and either may be resolved to afford enantiomerically purecompounds by methods known in organic synthesis. Preferred methodsinclude resolution by crystallization of diastereoisomeric salts derivedfrom acids 10 and a chiral amine base or the use of chiral stationaryphase liquid chromatography columns.

Reaction Scheme C illustrates a preferred method for the synthesis ofcompounds of general formula 2 wherein r is 1 and s is 2, such that theresulting heterocycle is a 4-aryl-3-piperidine-carboxylic acidderivative 17. The synthesis of 17 is similar to the one shown inreaction Scheme B, and may begin with either of the commerciallyavailable β-keto esters 11 or 12. Conversion of one of these startingmaterials to the N-BOC-protected piperidine 13 is performed as shown andthe resulting β-keto ester is subjected to the two-step arylationprotocol previously described to yield 15. Reduction of the double bondof 15 using conditions appropriate for obtaining either cis or trans 17is followed by ester hydrolysis which affords either a cis or trans4-aryl-3-piperidine-carboxylic acid of general formula 17 whichcorresponds to an acid of general formula 2 wherein r is 1 and s is 2.The cis or trans carboxylic acids of general formula 17 are produced asracemates and either may be resolved to afford enantiomerically purecompounds by methods known in organic synthesis. Preferred methodsinclude resolution by crystallization of diastereoisomeric salts derivedfrom the acids 17 and a chiral amine base or by the use of chiralstationary phase liquid chromatography columns.

The synthesis of the N-BOC protected carboxylic acids of general formula10 and 17 illustrated in reaction Schemes B and C are useful for thepreparation of title compounds of structural formula I bearing a varietyof R¹ substituents as noted above. For the synthesis of certain titlecompounds of structural formula I, for instance when it is desired thatR¹ be a tert-butyl group, it is preferable to incorporate that R¹substituent at an earlier stage of the synthesis. The synthesis of a1-substituted-3-ketopiperidine-4-carboxylic ester (21) is shown inreaction Scheme D. A primary amine 18 bearing a desired R¹ substituentlike a tert-butyl group is reacted with ethyl 4-bromobutyrate atelevated temperature in the absence of a solvent to afford theN-substituted ethyl 4-aminobutyrate 19. The amino ester 19 is thenalkylated a second time with ethyl bromoacetate in a high boiling inertsolvent such as toluene and in the presence of a base such as powderedpotassium carbonate. The resulting aminodiesters of general formula 20are then cyclized using an intramolecular Dieckmann reaction to affordpiperidines such as 21. The Dieckmann reaction is performed using astrong base such as potassium tert-butoxide or the like, in an aproticsolvent such as THF at temperatures between room temperature and theboiling point of the solvent. The resulting1-substituted-3-ketopiperidine-4-carboxylic ester 21 corresponds to acompound of general formula 5 shown in reaction Scheme B, where the BOCgroup is replaced with the desired R¹ substituent. The compounds ofgeneral formula 21 may then be converted to compounds of general formula2 where the R¹ substituent replaces the BOC group using the reactionsequence illustrated in reaction Scheme B.

When it is desirable to synthesize a compound of general formula 17wherein the BOC group is replaced with a substituent group R¹, areaction sequence similar to the one illustrated in reaction Scheme Cmay be employed as shown in reaction Scheme E. An amine 18 bearing thedesired R¹ substituent is first subjected to a Michael addition withexcess ethyl acrylate in the presence of a solvent such as THF orethanol. The resulting diester 22 is then converted to a1-substituted-4-ketopiperidine-3-carboxylic ester 23 using anintramolecular Dieckmann reaction under conditions similar to thoseillustrated in reaction Scheme C. The substituted piperidine 23corresponds to a compound of general formula 13 shown in reaction SchemeC, wherein the BOC group is replaced with the desired R¹ substituent.The compounds of general formula 23 may then be converted to compoundsof general formula 2 where the R¹ substituent replaces the BOC groupusing the methodology illustrated in reaction Scheme C.

Reaction Scheme F illustrates a strategy for the synthesis of compoundsof general formula 2 when the values of r and s are selected such thatthe resulting heterocycle is a 3-aryl-4-pyrrolidine carboxylic acidderivative (29). The preferred method for the synthesis of compounds ofgeneral formula 29 involves the azomethine ylid 3+2 cycloadditionreaction of an azomethine ylid precursor of general formula 25 and asubstituted cinnamic ester 24. The azomethine cycloaddition reaction of24 and 25 affords the 3,4-disubstituted pyrrolidine 26, and thestereochemical relationship of the substituents on the newly formedpyrrolidine ring is determined by the stereochemistry of the double bondin the cinnamate ester 24. Thus the trans ester 24 affords a trans3,4-disubstituted pyrrolidine of formula 26 as shown. The correspondingcis cinnamate ester affords a cis 3,4-disubstituted pyrrolidine ofgeneral formula 26. Cis or trans 3-arylpyrrolidine-4-carboxylic estersof general formula 26 may be resolved to afford enantiomerically purecompounds using a method such as resolution by crystallization of thediastereoisomeric salts derived from 26 and a chiral carboxylic acid, ordirectly by the use of chiral stationary phase liquid chromatographycolumns. Reaction Scheme F illustrates the case where a trans cinnamicester 24 is converted to a trans 3,4-disubstituted pyrrolidine 26 andits subsequent resolution affords the enantiomerically pure transpyrrolidine esters 27 and 28. Finally, the esters of general formula 26(or their pure enantiomers 27 and 28) are hydrolyzed to thecorresponding amino acid hydrochlorides of general formula 29 as shownat the bottom of reaction Scheme F.

Amino acids of general formula 29 are zwitterionic. Therefore it is insome cases difficult to achieve efficient separation and purification ofthese compounds from aqueous reactions or workups. In these cases it ispreferred to effect the hydrolysis using a reagent such potassiumtrimethylsilanolate in diethyl ether. Under these conditions thepotassium salt of the carboxylic acid is produced which affords aneasily isolated precipitate in ether. The resulting salt is thenconverted to the corresponding amino acid hydrochloride by treatmentwith excess hydrochloric acid in a suitable solvent such as ethylacetate. Alternatively, esters such as 26 may be converted directly tothe amino acid hydrochlorides 29 under acidic hydrolysis conditions. Thehydrolysis of the ester 26 is achieved by prolonged reaction withconcentrated hydrochloric acid at an elevated temperature. For example,this reaction may be conducted in 8 M hydrochloric acid at refluxovernight. The reaction mixture is then cooled and evaporated in vacuoto afford the amino acid hydrochloride 29. The amino acid hydrochloridesof general formula 29 correspond to an amino acid hydrochloride ofgeneral formula 2 wherein both r and s are 1 and may be employeddirectly in the amide bond coupling step illustrated in reaction SchemeA to produce the compounds of the present invention of structuralformula I.

Another preferred method for the synthesis of enantiomerically pure3-arylpyrrolidine-4-carboxylic acid derivatives is illustrated inreaction Scheme G. In this synthetic method, a substituted cinnamic acidof general formula 29 is first derivatized with a chiral auxilliary suchas (S)-(−)-4-benzyl-2-oxazolidinone (30). The acylation of chiralauxiliary 30 with cinnamic acids of formula 29 is performed by initialactivation of the acid to afford a mixed anhydride. Typically acids ofgeneral formula 29 are reacted with an acid chloride such as pivaloylchloride in the presence of a base such as triethylamine and in asuitable aprotic solvent such as THF. The intermediate cinnamyl-pivaloylanhydride is converted to the product 31 by reaction with theoxazolidinone 30 in the presence of lithium chloride, an amine base suchas triethylamine and in a solvent such as THF, and the reaction isconducted at temperatures between −20° C. and room temperature forperiods of 1–24 hours. Alternatively, the oxazolidinone 30 may bedeprotonated with a strong base such as n-butyllithium in THF at lowtemperatures such as −78° C. and then reacted with a mixed anhydrideobtained from acid 29 and an acid chloride like pivaloyl chloride asnoted above. The cinnamyl oxazolidinone of general formula 31, which isproduced by either of these methods, is then reacted with the azomethineylid precursor 25 in a manner similar to that described in reactionScheme F, and the products of the reaction are the substitutedpyrrolidines of general formulas 33 and 34 as shown. The products 33 and34 are diastereoisomers of each other and may therefore be separated bystandard methods such as recrystallization or by liquid chromatographyon a solid support such as silica gel. As discussed above, if the cisisomer of the cinnamic acid of general formula 29 is employed in thefirst step of reaction Scheme G, then a cis isomer of the substitutedcinnamyl oxazolidinone 31 is produced. If such a cis cinnamyloxazolidinone is then subjected to the azomethine ylid cycloadditionwith an azomethine ylid precursor of formula 25, the products are thediastereoisomeric cis-disubstituted pyrrolidines related to 33 and 34.

The azomethine ylid cycloaddition reactions shown in reaction Schemes Fand G are generally conducted with the commercially available azomethineylid precursor N-(methoxymethyl)-N-(trimethylsilylmethyl)-benzylamine(25, R¹=—CH₂Ph). When the R¹ substituent in the title compounds ofstructural formula I is chosen to be a group other than benzyl, it isgenerally preferable to remove the benzyl group from the substitutedpyrrolidine compound at this point, and replace it with a more readilyremoved protecting group such as an N-BOC group. Reaction Scheme Hillustrates this process with a generalized 3,4-disubstitutedpyrrolidine of formula 32. The preferred method for removal of theN-benzyl group from compounds of general formula 32 will depend upon theidentity of the R³ substituents. If these substituents are unaffected byhydrogenation conditions, then the N-benzyl group may be removed byhydrogenolysis using a palladium on carbon catalyst in a solvent such asethanol and in the presence of hydrogen gas or a hydrogen donor such asformic acid. Occasionally it may be preferred that one of thesubstituents R³ be a halogen or another substituent defined above whichwould be reactive under hydrogenation conditions. In these cases, thecompound of general formula 32 is reacted with 1-chloroethylchloroformate in an inert solvent such as toluene at temperaturesbetween room temperature and 110° C. (Olafson, R. A. et al. J. Org.Chem. 1984, 49, 2081). The toluene is then removed, and the residue isheated in methanol for a period of 15–60 minutes, and the product is thedebenzylated pyrrolidine of general formula 35. The resultingpyrrolidine 35 is then protected as its tert-butyl carbamate (36) usingBOC anhydride in the presence of a base and a suitable solvent. Forexample, this can be accomplished in a two phase mixture of chloroformand aqueous sodium bicarbonate as shown in reaction Scheme H.

The oxazolidinone chiral auxilliary is next hydrolyzed from thepyrrolidines of general formula 36 as shown at the bottom of reactionScheme H. The hydrolysis reaction is accomplished using lithiumhydroperoxide generated in situ from lithium hydroxide and 30% aqueoushydrogen peroxide. The reaction is typically conducted in a solventsystem such as aqueous THF, and the reaction is performed attemperatures between 0° C. and room temperature for a period of 1–6hours. The resulting carboxylic acids of general formula 37 correspondto carboxylic acids of general formula 2 where both r and s are 1. Usingthe methodology presented in reaction Scheme A, the compounds of generalformula 37 may then be converted to the compounds of the presentinvention of structural formula I.

As noted previously in the discussion of reaction Scheme D, it mayoccasionally be preferable to incorporate the R¹ substituent into thesubstituted pyrrolidine of general formula 37 at an earlier stage of thesynthesis, for instance when it is desired that R¹ be a tert-butylgroup. In such cases, it is possible to utilize an azomethine ylidprecursor (25) bearing the desired R¹ substituent in the cycloadditionreactions illustrated in reaction Schemes F and G. Reaction Scheme Iillustrates the preparation of azomethine precursors of formula 25starting with amines of general formula 18. Reaction of the amine offormula 18 with chloromethyltrimethylsilane at high temperature and inthe absence of solvent affords the N-trimethylsilylmethyl-substitutedamine of general formula 38. Subsequent reaction of 38 with aqueousformaldehyde in the presence of methanol and a base such as potassiumcarbonate then affords the generalized ylid precursor 25 which can beutilized in the cycloaddition reactions discussed above.

Reaction Schemes J and K illustrate additional methods for the synthesisof the 4-substituted piperidines of general formula 1 which are requiredin the amide bond coupling step illustrated in reaction Scheme A. Asshown in Reaction Scheme J, treatment of an ethanol solution ofcarboxylic acid 39, wherein R is hydrogen, C₁–C₆ alkyl or C₁–C₃polyfluoroalkyl, with a chlorinating agent such as thionyl chloride at atemperature of 65–78° C., preferably 78° C., for a period of 12–24 hoursgives the corresponding ethyl ester derivative 40. Ester 40 can befurther reacted with a strong reducing agent such lithium aluminumhydride, diisobutylaluminum hydride or equivalent hydride sources in aninert organic solvent such as tetrahydrofuran at 0–25° C. for a periodof 2–12 hours to provide alcohol 41. Hydrogenation of the aromatic ringin 41 is effected by treatment with hydrogen at a pressure of 1500pounds per square inch in an inert solvent such as acidic methanol at atemperature of 100° C. for a period of 15–24 hours. Suitable catalystsfor this hydrogenation reaction include rhodium on alumina and theproduct is a cyclohexyl substituted derivative of general formula 42.Protection of the amine as the tert-butyl carbamate by treatment withdi-tert-butyl dicarbonate and an amine base such as triethylamine,N,N-diisopropylethylamine or the like in an inert organic solvent suchas methanol at room temperature for a period of 10–14 hours gives 43.

As shown in Reaction Scheme K, alcohols of general formula 44 can beconverted to the corresponding aldehydes 45 by treatment with a mildoxidizing agent such as tetrapropylammonium perruthenate (TPAP) incatalytic amounts along with a re-oxidant such as 4-methylmorpholineN-oxide (NMMO) in an inert organic solvent such as methylene chloride ata temperature of 0–25° C. for a period of 2–6 hours. Aldehydes 45 may becondensed with an amine such as 2-amino-2-methyl-1-propanol by mixingthe two agents in a solvent such as toluene, benzene or the like alongwith an acid catalyst such as acetic acid, p-toluenesulfonic acid or thelike at refluxing temperature to allow for azeotropic removal of thewater formed in the reaction which furnishes imine 46. Reduction of 46to the amino alcohol 47 can be effected by treatment with hydrogen andan appropriate catalyst such as platinum oxide on carbon, palladium oncarbon, palladium hydroxide on carbon or the like with or without anacid catalyst such as acetic acid in an inert organic solvent such asacetic acid, methanol, and ethanol at room temperature for a period of8–24 hours. Compound 47 can he converted to the correspondingoxazolidinone 48 by treatment with an appropriate acylating agent suchas triphosgene along with an amine base such asN,N-diisopropylethylmine, triethylamine or the like, and a catalyst suchas 4-dimethylaminopyridine in an inert organic solvent such as methylenechloride at a temperature of 0–25° C. for a period of 24 hours. Finally,deprotection of the piperidine nitrogen by treatment with a protic acidsuch as hydrochloric acid, trifluoroacetic acid or the like in an inertorganic solvent such as methylene chloride at or around room temperaturefor a period of 8–24 hours provides the desired amine 49.

Reaction Scheme L illustrates general methods for the elaboration of anR¹ substituent following assembly of a compound of structural formula I(wherein R¹=BOC) as described in reaction Scheme A. The N-BOC protectedcompound of structural formula I is first deprotected under acidicconditions for instance by treatment with hydrochloric acid in ethylacetate or using trifluoroacetic acid in methylene chloride. Theresulting heterocyclic compound of structural formula I (R¹=H) may thenbe subjected to one of several alkylation strategies known in organicchemistry. For instance, compounds (I) (R¹=H) may be utilized in areductive amination reaction with a suitable carbonyl containing partner(50). The reductive amination is achieved by initial formation of animine between the amine of formula I (R¹=H) and either an aldehyde orketone of formula 50. The intermediate imine is then treated with areducing agent capable of reducing carbon-nitrogen double bonds such assodium cyanoborohydride or sodium triacetoxyborohydride and an alkylatedproduct of structural formula I is produced. Alternatively, aheterocyclic compound of structural formula (I) (R¹=H) may be directlyalkylated using an alkylating agent such as 51 in a polar aproticsolvent such as DMF. In this reaction, the substituent Z of compound 51is a good leaving group such as a halide, mesylate or triflate and theproduct is the compound of structural formula I bearing the R¹substituent.

Preparation of 4-Substituted Piperidine Intermediates:

The preparation of other 4-substituted piperidine intermediates ofgeneral formula 1 for coupling with the carboxylic acids of generalformula 2 as shown in Scheme A below is disclosed in PCT InternationalApplication WO 00/74679 (14 Dec. 2000), which is incorporated byreference herein in its entirety. The preparation of additional4-substituted piperidine intermediates needed to derive the compounds ofthe present invention is provided below.

To a solution of 4-cyclohexyl4-formyl-N-(tertbutyloxycarbonyl)-piperidine (2.56 g, 8.68 mmol) intoluene (100 ml) was added acetic acid (2 ml) and1-amino-1-cyclopentanemethanol (1.0 g, 8.68 mmol). After refluxing byusing a Dean-Stark apparatus for 11 hours, the reaction mixture wasconcentrated. The residue was dissolved in acetic acid (70 ml) andhydrogenated overnight in the presence of platinum oxide (500 mg) undera balloon atmosphere of hydrogen gas. The catalyst was filtered off andsolvent was removed to give a colorless oil, which was dissolved inmethanol and made basic by addition of NaOH (5N, 4 ml) and concentrated.The residue was partitioned between water and CH₂Cl₂, the two layersseparated, and the aqueous layer extracted with CH₂Cl₂. The combinedorganic extracts were washed with brine, dried over MgSO₄ andconcentrated to give the title compound as a colorless oil (2.1 g).

MS: calc.for C₂₃H₄₂N₂O₃: 394.3; Found: 395 (M+1), 417 (M+Na).

To a solution of Intermediate 1 (2.1 g, 5.33 mmol) in CH₂Cl₂ (70 ml) at0° was added DMAP (0.65 g, 5.33 mmol), DIEA (3.76 ml, 21.3 mmol)followed by slow addition of phosgene (4.1 ml, 8.0 mmol). After stirringthe reaction mixture for one hour at 0° C., the ice-water bath wasremoved and the reaction mixture was continued to stir at roomtemperature overnight. The mixture was diluted with CH₂Cl₂, washed withwater and brine, dried over MgSO₄ and concentrated to give crudeproduct, which was purified by column chromatography on silica gel (2%EtOAc/CH₂Cl₂ to 5% EtOAc/CH₂Cl₂) to give the title compound as a whitesolid (1.2 g).

MS: calc.for C₂₄H₄₀N₂O₄: 420.3; Found: (M+1), (M+Na).

To the Intermediate 2 (1.2 g) was added hydrogen chloride (4.0 M indioxane). The reaction mixture was stirred at room temperature for 30minutes and the solvent was removed in vacuo to afford the titlecompound (1.2 g).

MS: calc.for C₁₉H₃₂N₂O₂: 320.3; Found: 321.1 (M+H).

Intermediate 4 was prepared from (S)-(+)-2-amino-1-propanol in ananalogous manner to the one described for the preparation ofIntermediate 1.

MS: calc.for C₂₀H₃₈N₂O₃: 354; Found: 355 (M+H).

Intermediate 5 was prepared from Intermediate 4 in an analogous mannerto the one described for the preparation of Intermediate 2.

MS: calc. for C₂₁H₃₆N₂O₄: 380.3; Found: 381 (M+H).

Intermediate 6 was prepared from Intermediate 5 in an analogous mannerto the one described for the preparation of Intermediate 3.

MS: calc. for C₁₆H₂₈N₂O₂: 280.3; Found: 281 (M+H).

To a suspension of 1-aminocyclopropane-1-carboxylic acid (2.8 g, 27.7mmol) in THF (20 ml) was added borane-tetrahydrofuran complex (100 ml,100 mmol) slowly under nitrogen at room temperature. The reactionmixture was stirred at 70° C. overnight, then cooled to 0° C. Afteraddition of methanol (12.2 ml, 300 mmol), the mixture was allowed tostir for 30 minutes. Then acetic acid (1.6 ml, 27.7 mmol) was added. Thereaction mixture was concentrated to provide the title compound as acolorless oil (3.0 g).

Intermediate 8 was prepared from Intermediate 7 in an analogous mannerto the one described for the preparation of Intermediate 1.

MS: calc. for C₂₁H₃₈N₂O₃: 366.3; Found: 367 (M+H).

To a solution of Intermediate 8 (0.8 g, 2.18 mmol) in CH₂Cl₂ (40 ml) at0° was added DMAP (0.266 g, 2.18 mmol), DIEA (1.52 ml, 8.74 mmol) andtriphosgene (0.648 g, 2.18 mmol). After stirring the reaction mixturefor one hour at 0° C., the ice-water bath was removed and the reactionmixture was allowed to stir at r.t. overnight. The mixture was dilutedwith CH₂Cl₂, washed with water and brine, dried over MgSO₄ andconcentrated to give crude product, which was purified by columnchromatography on silica gel (10% CH₂Cl₂/EtOAc) to give the titlecompound as a colorless oil (0.13 g).

ESI-MS: calc. for C₂₂H₃₆N₂O₄: 392; Found: 393 (M+1).

Intermediate 10 was prepared from Intermediate 9 in an analogous mannerto the one described for the preparation of Intermediate 3.

MS: calc. for C₁₇H₂₈N₂O₂: 292.2; Found: 293 (M+H).

To a solution of the alcohol (9.41 g, 31.6 mmol) in CH₂Cl₂ (100 ml) at0° C. containing molecular sieves (2 g) and 4-methylmorpholine N-oxide(NMMO) (4.449 g, 37.98 mmol) was added TPAP (1.12 g, 3.16 mmol). Afterstirring the reaction mixture at 0° C. for 0.5 h, the reaction mixturewas warmed to room temperature and stirred further for 5 hrs. Thereaction mixture was concentrated to half the volume, diluted withhexane (250 ml), filtered through a silica gel pad and concentrated togive pure title compound (9.4 g).

To a solution of the aldehyde (2 g, 6.7 mmol) in toluene (50 ml) wasadded acetic acid (500 μl). After stirring the reaction mixture atreflux temperature using Dean Stark apparatus for 8 hrs, the mixture wasconcentrated and dissolved in acetic acid (30 ml). To the mixture wasadded PtO₂ (500 mg) which was stirred under an atmosphere of H₂overnight. The reaction mixture was flushed with nitrogen, filtered andconcentrated to give the title compound (2 g).

To a solution of the amino alcohol (4.96 g, 13.47 mmol) in CH₂Cl₂ at 0°C. containing DIEA (6.98 g, 53.9 mmol), DMAP (1.64 g, 13.47 mmol) wasadded slowly a toluene solution of phosgene (1.93M, 10.47 ml, 20.21mmol). After stirring the reaction mixture for 1 hr at 0° C., thetemperature was raised to room temperature and stirred further for 2hrs. The reaction mixture was diluted with CH₂Cl₂, washed with water,brine, dried and concentrated. The residue was purified by columnchromatography over silica gel (5% EtOAc/CH₂Cl₂) to give pure product(3.95 g).

To a solution of Intermediate 13 (3.95 g) in CH₂Cl₂ was added 5 ml of asaturated HCl solution in EtOAc. After stirring the reaction mixture for30 min at room temperature, the solvent was removed and the residuelyophilized from a benzene/methanol solution to afford the titlecompound (3.85 g).

Step A

To a 500-mL round-bottom flask equipped with a Dean Stark trap andmagnetic stirrer was added 1-Boc-4-piperidone (M-1) (20.0 g, 100 mmol),cyanoacetic acid ethyl ester (10.6 mL, 100 mmol), NH₄OAc (0.77 g, 10mmol), HOAc (0.57 mL, 10 mmol), and benzene (200 mL). The mixture wasstirred at reflux temperature overnight. After cooling to roomtemperature, the volatiles were removed under reduced pressure, and theresidue was purified by flash column chromatography with 20% EtOAc inhexane as eluent to give M-2 as white solid (21.6 g).

ESI-MS: Calcd. for C₁₅H₂₂N₂O₄: 294; Found: 317 (M⁺+Na).

Step B

To a suspension of CuCN (3.28 g, 36.3 mmol) in dry THF (100 mL) wasadded cyclohexylmagnesium chloride (36.6 mL, 73.2 mmol, 2.0 N in ether).The resulting suspension was stirred at −50° C. for 30 min and thenwarmed up to room temperature. After stirring for 1 h, a solution ofcompound M-1 (5.40 g, 18.3 mmol) in 50 mL of THF was cannulated into themixture over 2 min. The mixture was stirred at −50° C. for 1 h and thenkept at −25° C. overnight. The mixture was slowly warmed to −10° C. andquenched with saturated aqueous NH₄Cl (50 mL) and water (50 mL),extracted with EtOAc (2×250 mL). The combined organic extracts werewashed three times with water, 1 N HCl, saturated aqueous NaHCO₃, driedover MgSO₄, filtered, and evaporated to give compound M-3 as a colorlessoil (7.12 g).

ESI-MS: Calcd. for C₂₁H₃₄N₂O₄: 378; Found: 401 (M⁺+Na).

Step C

A mixture of M-3 (6.91 g, 18.3 mmol), LiCl (1.09 g, 25.6 mmol), water(1.40 mL), and DMSO (100 mL) was stirred at 160° C. for 1 h. Aftercooling to room temperature, the mixture was poured into water (800 mL)and extracted with Et₂O (4×250 mL). The combined organic layers werewashed with brine, dried over anhydrous Na₂SO₄, filtered, andconcentrated. The residue was purified by flash column chromatographywith 20% EtOAc in hexane as eluent to give compound M-4 as a colorlessoil (2.83 g).

ESI-MS: Calcd. for C₁₈H₃₀N₂O₂: 306; Found: 329 (M⁺+Na).

Step D

To a solution of 4.0 N HCl in dioxane (30 mL, 120 mmol) was added M-4(2.60 g, 8.48 mmol). The mixture was stirred at room temperature for 1 hand the volatiles were removed under reduced pressure. The residue wasdissolved in a concentrated HCl (100 mL). The mixture was stirredovernight at reflux temperature. After cooling to room temperature, thevolatiles were removed under reduced pressure to give the compound M-5as a yellow solid (2.42 g).

ESI-MS: Calcd. for C₁₃H₂₃NO₂: 225; Found: 226 (M⁺+1)

Step E

To a solution of compound M-5 (1.91 g, 8.48 mmol) in dioxane (50 mL) andwater (50 mL, containing 5.0 mL 5.0 N NaOH, 25 mmol) was addeddi-tert-butyl dicarbonate (2.22 g, 10.2 mmol). The mixture was stirredat room temperature for 4 h and the volatiles were removed under reducedpressure. The residue was quenched with a mixture of EtOAc (200 mL) and1 N HCl (50 mL). The layers were separated and the aqueous layer wasextracted three times with EtOAc. The combined organic layers were driedover anhydrous Na₂SO₄, filtered, and evaporated to give M-6 as a whitesolid (2.97 g).

ESI-MS: Calcd. for C₁₈H₃₁NO₄: 325; Found: 326 (M⁺+1)

Step F

Compound M-6 (1.0 g, 3.07 mmol) was dissolved in 30 mL of methylenechloride, and then diethylamine (0.38 mL, 3.68 mmol), DMAP (0.037 g,0.307 mmol), EDC (1.18 g, 6.14 mmol) were added. The resulting mixturewas stirred at room temperature overnight, and then diluted with 20 mLof CH₂Cl₂ and washed with 20 mL of 1N HCl solution, 20 mL of saturatedNaHCO₃ solution, 20 mL of H₂O, and 20 mL of saturated NaCl solution. Theorganic phase was dried over MgSO₄, filtered, and evaporated to give M-7(1.16 g).

ESI-MS: Calcd. for C₂₂H₄₀N₂O₃: 380; Found: 381 (M⁺+1)

Step G

To a solution of 4.0 N HCl in dioxane (30 mL, 120 mmol) was added M-7(1.16 g, 3.07 mmol). The mixture was stirred at room temperature for 1 hand the volatiles were removed under reduced pressure to give M-8 (0.99g).

ESI-MS: Calcd. for C₁₇H₃₂N₂O: 280; Found: 281 (M⁺+1)

Step A

To a solution of M-6 (0.18 g, 0.554 mmol) in 8.0 mL of dry TBF was addedborane-dimethyl sulfide complex (1.10 mL, 2.0 N in THF, 2.20 mmol). Themixture was stirred overnight and then quenched with MeOH. The volatileswere removed under reduced pressure to give N-1 (0.11 g).

ESI-MS: Calcd. for C₁₈H₃₃NO₃: 311; Found: 334 (M⁺+Na).

Step B

To a suspension of N-1 (0.11 g, 0.347 mmol), 4-methylmorpholine N-oxide(0.049 mg, 0.416 mmol), and molecular sieve in dry methylene chloride(5.0 mL) was added tetrapropylammonium perruthenate (0.012 g, 0.035mmol). After stirring for 30 min, the mixture was filtered through a padof silica gel and washed with ether. The organic solution was evaporatedto give compound N-2 as an oil (0.11 g).

ESI-MS: Calcd. for C₁₈H₃₁NO₃: 309; Found: 332 (M⁺+Na).

Step C

To a solution of N-2 (0.11 g, 0.35 mmol) in 3.0 mL of methylene chloridewas added diethylamine (0.072 mL, 0.70 mmol) and molecular sieves. Afterstirring for about 5 min, Na(OAc)₃BH (0.22 mg, 1.05 mmol) was added andthe mixture was stirred for 6 h at room temperature. After filtration ofmolecular sieves, the mixture was diluted with methylene chloride,washed twice with saturated aqueous NaHCO₃ solution, dried overanhydrous Na₂SO₄, filtered, and evaporated to give N-3 (0.080 g).

ESI-MS: Calcd. for C₂₂H₄₂N₂O₂: 366; Found: 367 (M⁺+1).

Step D

To a solution of 4.0 N HCl in dioxane (10 mL, 40 mmol) was addedcompound N-3 (0.080 g, 0.218 mmol). The mixture was stirred at roomtemperature for 1 h and the volatiles were removed under reducedpressure to give N4 (0.075 g).

ESI-MS: Calcd. for C₁₇H₃₄N₂: 266; Found: 227 (M⁺+1)

Step A

To a stirred solution of tert-butyl4-cyclohexyl-4-{[(methylsulfonyl)oxy]methyl}piperidine-1-carboxylate(O-1) (3 g, 8.0 mmol) in DMF (30 mL) at room temperature was addedsodium 2-methyl-2-propanethiolate (0.78 g, 8.0 mmol). The resultantsuspension was stirred at 60° C. for 18 h and then poured into water(150 mL) and extracted with diethyl ether (3×100 mL). The combinedorganic extracts were washed with brine, dried over Na₂SO₄ andconcentrated. Flash chromatography over silica (5% EtOAc in hexane)yielded O-2 (W=iPr) as a clear colorless oil (2.4 g).

Mass Spectrum (ESI): calcd for C₂₀H₃₇NO₂S: 355.25; Found: 378 (M⁺+Na).

Step B

To a stirred solution of O-2 (W=iPr) (2.4 g, 6.7 mmol) in methylenechloride (10 mL) at room temperature was added HCl (5N in dioxane) (50mL). The resultant solution was stirred at room temperature for 1 h.Volatiles were removed in vacuo to furnish O-3 (W=iPr) as a clearcolorless gum (1.9 g).

Mass Spectrum (ESI): calcd for C₁₅H₂₉NS: 255.20; Found: 256 (M⁺+1).

The piperidine intermediates O-3 (W=Me, Et, n-Pr, cyclopropylmethyl, andcyclobutyl) were prepared in an analogous manner to the one describedfor the preparation of4-cyclohexyl-4-[(isopropylthio)methyl]piperidinium chloride (O-3,W=iPr).

O-3 (W=Et): Mass Spectrum (ESI): calcd for C₁₄H₂₇NS: 241.19; Found: 242(M⁺+1).

O-3 (W=Me): Mass Spectrum (ESI): calcd for C₁₃H₂₅NS: 227.17; Found: 228(M⁺+1).

O-3 (W=n-Pr): Mass Spectrum (ESI): calcd for C₁₅H₂₉NS: 255.20; Found:256 (M⁺+1).

O-3 (W=cyclopropylmethyl): Mass Spectrum (ESI): calcd for C₁₆H₂₉NS:267.20; Found: 268 (M⁺+1).

O-3 (W=cyclobutylthio): Mass Spectrum (ESI): calcd for C₁₆H₂₉NS: 267.20;Found: 268 (M⁺+1).

Step A

To a solution of P-1 (0.745 g, 2.072 mmol) in methylene chloride (40 mL)at 0° C. was added DMF (1 mL) followed by the dropwise addition ofoxalyl chloride (1.14 mL of 2M solution in methylene chloride, 2.28mmol). The reaction was warmed to room temperature over one h, thenre-cooled to 0° C. before transferring to a rapidly stirring saturatedaqueous ammonium hydroxide solution (15 mL). The resulting mixture wasthen poured into methylene chloride (40 mL) and diluted with 1N NaOH (40mL). The layers were separated and the aqueous phase was extracted threetimes with methylene chloride. The combined organics were then washedwith water and brine, dried (sodium sulfate) and the volatiles removedin vacuo. Flash chromatography over silica (25% acetone/methylenechloride) yielded P-2 as a white foam (0.615 g).

Mass Spectrum (ESI): calcd for C₂₁H₃₀N₂O₃: 358.23; Found 359 (M⁺+1).

Step B

A solution of P-2 (0.150 g, 0.84 mmol) in N,N-dimethylformamide dimethylacetal (1 mL) was refluxed at 120° C. for 2 h, then cooled to roomtemperature. The reaction was then concentrated and the residue wasdissolved in acetic acid (1 mL). Ethyl hydrazine was then added and thereaction was heated at 95° C. for 3.5 h. The volatiles were then removedin vacuo and the reaction was partitioned between sodium bicarbonate andethyl acetate. The organics were collected, washed with water and brine,dried (sodium sulfate), and the volatiles removed in vacuo. Purificationby flash chromatography (0–15% acetone in methylene chloride) yieldedP-3 as a pale yellow oil (79 mg).

Mass Spectrum (ESI): calcd for C₂₄H₃₄N₄O₂: 410.27; Found 411 (M⁺+1).

Step C

To a solution of P-3 (79 mg) in methylene chloride was added 30% HBr inacetic acid (5 mL) and the reaction was stirred for two hours. Thevolatiles were removed, and the reaction was partitioned between 1N NaOHand methylene chloride. The organics were dried (sodium sulfate) andevaporated to afford P-4 as an oil (59 mg). Mass Spectrum (ESI): calcdfor C₁₆H₂₈N₄: 276.23; Found 277 (M⁺+1).

Step A

To a stirred solution of Q-1 (1.33 g, 4.5 mmol) in methylene chloride(12 mL) was added DMAP (0.14 g, 1.1 mmol) and 3-chloropivaloyl chloride(0.87 g, 5.6 mmol). The mixture was stirred 1 h, diluted with methylenechloride, washed with 1N HCl, the organic layer dried over MgSO₄ and thesolvent removed in vacuo to provide 2.1 g of Q-2 as an oil. ESI-MS calc.for C₂₂H₃₉ClN₂O₃: 414; Found 415 (M+H).

Step B

To a stirred solution of Q-1 (2.25 g, 5.42 mmol) in DMF (15 mL) wasadded NaH (0.52 g, 21.7 mmol) and heated to 70° C. for 16 h. The mixturewas quenched with MeOH and then water. The mixture was concentrated,diluted with EtOAc, washed with 2N HCl, brine, dried over MgSO₄ andevaporated. The product was purified by preparative HPLC (C18, 20×100mm, 50–100% acetonitrile) to provide 850 mg of Q-3 as a yellow solid.ESI-MS calc. for C₂₂H₃₈N₂O₃: 378; Found 379 (M+H).

Step C

Compound Q-3 (1.05 g, 1.92 mmol) was treated with HCl-EtOAc solution atroom temperature for 30 min. The mixture was evaporated to provide 690of Q-4 as a solid. ESI-MS calc. for C₁₇H₃₀N₂O: 278; Found 279 (M+H).

Step A

Compound R-1 was synthesized in a manner similar as Q-2, but using3-chloropropionyl chloride. ESI-MS calc. for C₂₀H₃₅ClN₂O₃: 386; Found387 (M+H).

Step B

Compound R-2 was synthesized from R-1 in a manner similar as Q-3. ESI-MScalc. for C₂₀H₃₄N₂O₃: 350; Found 351 (M+H).

Step C

Compound R-3 was synthesized from R-2 in a manner similar as Q-4. ESI-MScalc. for C₁₅H₂₆N₂O: 250; Found 251 (M+H).

Step A

Compound S-1 was synthesized in a manner similar as Q-2, but using4-chlorobutyryl chloride. ESI-MS calc. for C₂₁H₃₇ClN₂O₃: 400; Found 401(M+H).

Step B

Compound S-2 was synthesized from S-2 in a manner similar to Q-3. ESI-MScalc. for C₂₁H₃₆N₂O₃: 364; Found 365 (M+H).

Step C

Compound S-3 was synthesized from S-2 in a manner similar to Q-4. ESI-MScalc. for C₁₆H₂₈N₂O: 264; Found 265 (M+H).

Step A

To a stirred solution of S-2 (2.3 g, 6.3 mmol) in THF (20 mL) cooled to−78° C. was added lithium diisopropylamide (LDA) (2M solution in THF) (3eq) slowly via syringe over 20 min and stirring was continued for 1 h.Iodomethane was added and the mixture was stirred for 1 h. The reactionmixture was warmed to room temperature and stirring was continued anadditional 30 min. Subsequently, the reaction mixture was cooled againto −45° C. and another 1.5 eq. of LDA added, the mixture was stirred 15min, then an additional 1 eq. of iodomethane was introduced to thereaction mixture and the stirring continued 1 h. The reaction wasquenched with water, concentrated and partitioned between EtOAc/2N HCl,washed with brine, dried over MgSO₄, filtered and concentrated. Theresidue was chromatographed (silica, 1:4 EtOAc/hexane) to provide 720 mgof T-1 as a white solid. ESI-MS calc. for C₂₃H₄₀N₂O₃: 392; Found 393(M+H).

Step B

Compound T-2 was prepared from T-1 in a manner similar to Q-4. ESI-MScalc. for C₁₈H₃₂N₂O: 292; Found 293 (M+H).

The following Examples are provided to illustrate the invention and arenot to be construed as limiting the scope of the invention in anymanner.

EXAMPLE 1

(±)-trans4-({4-Cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidin-1-yl}carbonyl)-3-(4-fluorophenyl)-1-methylpiperidiniumtrifluoroacetateStep A; Preparation of tert-butyl(±)-trans-4-({4-cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidin-1-yl}carbonyl)-3-(4-fluorophenyl)piperidine-1-carboxylate

1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (47.7 mg,0.249 mmol) was added to a stirred mixture of4-cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidiniumchloride (54.9 mg, 0.166 mmol),(±)-trans-1-(tert-butoxycarbonyl)-3-(4-fluorophenyl)-piperidine-4-carboxylacid (70.7 mg, 0.216 mmol), 1-hydroxy-benzotriazole (33.6 mg, 0.249mmol) and N-methylmorpholine (54.8 μL, 0.498 mmol) in methylene chloride(2.1 mL) at ambient temperature. After approximately 18 h, the reactionmixture was poured into saturated aqueous sodium bicarbonate andextracted three times with methylene chloride. The combined organicextracts were washed with brine, dried (Na₂SO₄) and concentrated invacuo. The crude residue was used without further purification in thesubsequent reaction.

Step B: Preparation of(±)-trans-4-({4-cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidin-1-yl}carbonyl)-3-(4-fluorophenyl)piperidiniumtrifluoroacetate

A saturated solution of hydrogen chloride in ethyl acetate (2.0 mL) wasadded to a solution of crude product from step A in methylene chloride(1.0 mL) at room temperature. After 18 h, the volatiles were evaporatedin vacuo, and the crude residue purified by preparative reversed phasehigh pressure liquid chromatography on a YMC Pack Pro C18 column(gradient elution: 0–100% acetonitrile/water as eluent, 0.1% TFA asmodifier) to give the title compound as an off-white solid [MS: m/z 500(MH⁺)].

Step C: Preparation of(±)-trans-4-({4-cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidin-1-yl}carbonyl)-3-(4-fluorophenyl)-1-methylpiperidiniumtrifluoroacetate

Sodium cyanoborohydride (12.6 mg, 0.200 mmol) was added to a vigorouslystirred suspension of the product of step B (20.0 mg, 0.040 mmol),paraformaldehyde (20.0 mg), 4 Å sieves (20.0 mg) and acetic acid (45.8μL, 0.800 mmol) in tetrahydrofuran/methanol (1:3, 400 μL) at ambienttemperature. After 18 h, the reaction mixture was poured into saturatedaqueous sodium bicarbonate and extracted three times with methylenechloride. The combined organic extracts were washed with brine, dried(Na₂SO₄) and concentrated in vacuo. Purification of the crude residue bypreparative reversed phase high pressure liquid chromatography on YMCPack Pro C18 column (gradient elution; 0–100% acetonitrile/water aseluent, 0.1% TFA as modifier) provided the title compound (12 mg) as anoff-white solid (12.0 mg); MS: m/z 514 (MH⁺).

Following a procedure similar to that described above for Example 1, thefollowing compounds can be prepared:

Parent Ex. Relative stereo. Ion # (3,4) R¹ R² m/z 2 trans (RS,RS) —H4-fluorophenyl 500 3 trans (S,S) —H 4-fluorophenyl 500 4 trans (R,R) —H4-fluorophenyl 500 5 trans (RS,RS) —CH₂C(O)Ot-Bu 4-fluorophenyl 614 6trans (RS,RS) —CH₂C(O)OH 4-fluorophenyl 558 7 trans (R,R) isopropyl4-fluorophenyl 542 8 trans (R,R) methyl 4-fluorophenyl 514 9 trans (R,R)n-propyl 4-fluorophenyl 542 10 trans (R,R) ethyl 4-fluorophenyl 528 11trans (R,R) CH(CH₃)CH₂OMe 4-fluorophenyl 572 12 trans (RS,RS) —H4-chlorophenyl 516 13 trans (RS,RS) —H 4-methoxyphenyl 512 14 trans(S,S) methyl 4-chlorophenyl 530 15 trans (R,R) methyl 4-chlorophenyl 53016 trans (RS,RS) —H 4-methylphenyl 496 17 trans (RS,RS) —H 4-(4′-chloro-592 phenyl)phenyl 18 trans (RS,RS) isopropyl 4-chlorophenyl 558 19 trans(R,R) isopropyl 4-chlorophenyl 559 20 trans (S,S) isopropyl4-chiorophenyl 559 21 trans (RS,RS) cyclobutyl 4-chlorophenyl 570 22trans (RS,RS) n-propyl 4-chlorophenyl 558 23 trans (RS,RS) ethyl4-chlorophenyl 544 24 trans (R,R) —C(═NH)NH₂ 4-fluorophenyl 543 25 trans(R,R) —C(═NH)NH₂ 4-chlorophenyl 559 26 trans (R,R) —CH₂CH₂NH₂4-chlorophenyl 560 27 trans (R,R) —CH₂CH₂NH₂ 4-fluorophenyl 544 28 trans(RS,RS) —H 4-chloro-3- 534 fluorophenyl 29 trans (RS,RS) isopropyl4-chloro-3- 576 fluorophenyl 30 trans (R,R) —C(═NH)CH₃ 4-fluorophenyl541 31 trans (RS,RS) —H 3-chloro-4- 535 fluorophenyl 32 trans (RS,RS)isopropyl 3-chloro-4- 577 fluorophenyl 33 trans (RS,RS) ethyl3-chloro-4- fluorophenyl 34 trans (RS,RS) —H 2,4-dichlorophenyl 551 35trans (RS,RS) isopropyl 2,4-dichlorophenyl 593 36 trans (RS,RS) —H3,4-dichlorophenyl 551 37 trans (RS,RS) isopropyl 3,4-dichlorophenyl 59338 trans (RS,RS) —H 2,4-difluorophenyl 519 39 trans (RS,RS) isopropyl2,4-difluorophenyl 561 40 trans (RS,RS) ethyl 2,4-difluorophenyl 546 41trans (RS,RS) —H 3,4-difluorophenyl 519 42 trans (RS,RS) isopropyl3,4-difluorophenyl 560 43 trans (RS,RS) ethyl 3,4-difluorophenyl 546 44trans (RS,RS) —H 4-chloro-2- 535 fluorophenyl 45 trans (RS,RS) isopropyl4-chloro-2- 577 fluorophenyl 46 trans (RS,RS) ethyl 4-chloro-2- 562fluorophenyl 47 trans (R,R) —CH₂CF₃ 4-chlorophenyl 582 48 trans (R,R)—CH(CH₃)CH₂CH₃ 4-fluorophenyl 556 49 trans (RS,RS) —CH₂CH₂N(CH₃)₂4-chlorophenyl 587

EXAMPLE 50

(±)-trans-3-(4-Chlorophenyl)4{-[4-cyclohexyl-4-(ethoxycarbonyl)piperidin-1yl]carbonyl}-1-isopropylpiperidiniumtrifluoroacetateStep A: Preparation of 4-(ethoxycarbonyl)-3-oxopiperidinium chloride

A mixture of ethyl 1-benzyl-3-oxopiderine-4-carboxylate hydrochloride(20.0 g, 67.0 mmol) and 10% Pd/C (2.00 g; Degussa Type E101) inethanol/water (1:1; 300 mL) was hydrogenated at 50 psi for 4 h. Theresulting mixture was filtered through celite® and the filtrateevaporated in vacuo to give the title compound as a brown solid (67.0mmol).

Step B: Preparation of 1-tert-butyl 4-ethyl3-oxopiperidine-1,4-dicarboxylate

Di-tert-butyl-dicarbonate (17.5 g, 80.4 mmol) was added in one portionto a stirred mixture of the crude product of step A (67.0 mmol), sodiumbicarbonate (6.20 g, 73.7 mmol) and sodium chloride (11.7 g, 201 mmol)in water/chloroform (1:2; 300 mL) and the resulting mixture heated at60° C. for 3 h. After cooling to room temperature, the organic phase wasseparated and the aqueous phase extracted three times with chloroform.The combined organic extracts were washed with brine, dried (MgSO₄) andconcentrated in vacuo. The crude residue (27.1 g) was used withoutfurther purification in the subsequent reaction.

Step C: Preparation of 1-tert-butyl 4-ethyl5-{[(trifluoromethyl)-sulfonyl]oxy}-3,6-dihydropyridine-1,4(2H)-dicarboxylate

Trifluoromethanesulfonic anhydride (12.4 mL, 73.7 mmol) was added overapproximately 0.1 h, via syringe, to a stirred solution of the productof step B (27.1 g, 67.0 mmol) and N,N-diisopropylethylamine (14.0 mL,80.4 mmol) in methylene chloride (250 mL) at −78° C. After allowing towarm to ambient temperature overnight, the reaction mixture was quenchedwith saturated aqueous sodium bicarbonate, poured into water andextracted three times with methylene chloride. The combined organicextracts were washed with brine, dried (MgSO₄) and concentrated invacuo. Purification of the residue by flash chromatography on silica gel(gradient elution; 0–20% ethyl acetate/hexanes as eluent) afforded thetitle compound as an amber colored oil (17.6 g).

Step D: Preparation of 1-tert-butyl 3-ethyl4-(4-chlorophenyl)-5,6-dihydropyridine-1,3(2H)-dicarboxylate

A vigorously stirred suspension of the product of step C (1.00 g, 2.48mmol), 4-chlorophenylboronic acid (0.427 g, 2.73 mmol) and[1,1′-bis(diphenylphosphino)-ferrocene)dichloropalladium(II) (0.102 g,0.124 mmol) in toluene/ethanol (3:2; 24.0 mL) was degassed via threevacuum/nitrogen ingress cycles and then heated to approximately 80° C.Aqueous 2 M sodium carbonate (3.10 mL, 6.20 mmol) was added dropwise viasyringe and the resulting mixture maintained at reflux overnight. Aftercooling to ambient temperature, the reaction mixture was diluted withethyl acetate and filtered through celite®. The filtrate was poured intowater and extracted three times with ethyl acetate. The combined organicextracts were washed with brine, dried (MgSO₄) and concentrated invacuo. Purification of the residue by medium pressure liquidchromatography on silica gel (gradient elution; 0–15% ethylacetate/hexanes as eluent) furnished the title compound as a colorlessoil (0.828 g).

Step E: Preparation of (±)-1-tert-butyl 3-ethyl4-(4-chloro-phenyl)piperidine-1,3-dicarboxylate

Magnesium metal (1.23 g, 51.0 mmol) was added in three portions overapproximately 0.3 h to a stirred solution of the product of step D (1.85g, 5.1 mmol) in methanol (40 mL) at ambient temperature. After stirringovernight, the reaction mixture was poured into 1 N hydrochloric acid(100 mL) and extracted three times with ethyl acetate. The combinedorganic extracts were washed with saturated sodium bicarbonate, brine,dried (MgSO₄) and concentrated in vacuo. Purification of the residue bymedium pressure liquid chromatography on silica gel (gradient elution;0–25% ethyl acetate/hexanes as eluent) provided the title compound(mixture of cis/trans diastereoisomers) as a colorless oil (1.5 g).

Step F: Preparation of(±)-trans-1-(tert-butoxycarbonyl)-3-(4-chlorophenyl)piperidine-4-carboxylicacid

Excess sodium metal was added to a stirred solution of the product ofstep E (1.5 g, 4.1 mmol) in methanol (20 mL) at ambient temperature, andthe resulting solution heated to 75° C. After approximately 1 h, 5 Msodium hydroxide (5.0 mL) was added and the reaction mixture heated to100° C. for an additional hour. After cooling to room temperature, thereaction mixture was acidified to pH 5 with 2 N hydrochloric acid andextracted three times with methylene chloride. The combined organicextracts were washed with brine, dried (MgSO₄) and concentrated invacuo, to give the title compound as a colorless solid (1.3 g). Thecrude product was used without further purification in the subsequentreaction.

Step G: Preparation of(±)-trans-3-(4-chlorophenyl)-4-{[4-cyclohexyl-4-(ethoxycarbonyl)piperidin-1-yl]carbonyl}piperidiniumtrifluoroacetate

1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (0.034 g,0.177 mmol) was added to a stirred mixture of the crude product of stepF (0.040 g, 0.118 mmol), 4-cyclohexyl-4-(ethoxycarbonyl)piperidiniumchloride (0.049 g, 0.177 mmol), 1-hydroxybenzotriazole (0.024 g, 0.177mmol) and N-methylmorpholine (0.020 mL, 0.177 mmol) in methylenechloride (0.5 mL) at ambient temperature. After approximately 18 h, thereaction mixture was poured into water/saturated sodium bicarbonate(1:1) and extracted three times with methylene chloride. The combinedorganic extracts were washed with brine, dried (Na₂SO₄) and concentratedin vacuo. A saturated solution of hydrochloric acid in ethyl acetate(1.0 mL) was added to a solution of the crude amide in methylenechloride (1.0 mL) at room temperature. After 18 h, the volatiles wereevaporated in vacuo, and the crude residue purified by preparativereversed phase high pressure liquid chromatography on YMC Pack Pro C18phase (gradient elution; 0–100% acetonitrile/water as eluent, 0.1% TFAas modifier) to give the title compound (0.034 g) as an off-white solid[MS: m/z 461 (MH⁺)].

Step H: Preparation of(±)-trans-3-(4-chlorophenyl)-4-{[4-cyclohexyl-4-(ethoxycarbonyl)piperidin-1-yl]carbonyl}-1-isopropylpiperidiniumtrifluoroacetate

Sodium triacetoxyborohydride (34.5 mg, 0.163 mmol) was added to astirred solution of the product of step G (25.0 mg, 54.2 mmol), acetone(23.9 mL, 0.325 mmol) and acetic acid (9.3 mL, 0.163 mmol) in methylenechloride (0.5 mL) at ambient temperature. After 18 h, the reactionmixture was poured into saturated aqueous sodium bicarbonate andextracted three times with methylene chloride. The combined organicextracts were washed with brine, dried (Na₂SO₄) and concentrated invacuo. Purification of the residue by preparative reversed phase highpressure liquid chromatography on YMC Pack Pro C18 phase (gradientelution; 0–100% acetronirile/water as eluent, 0.1% TFA as modifier)afforded the title compound as an off-white solid [MS: m/z 503 (MH⁺)].

Following a procedure sirnilar to that described above for Example 50,the following compounds can be prepared:

Relative stereo. Parent Ion Ex. # (3,4) R¹ R³ X m/z 51 trans (RS,RS) —H—F

472 52 trans (R,R) —H —F

472 53 trans (RS,RS) —H —Cl

488 54 trans (RS,RS) —H —F

445 55 trans (S,S) —H —F

445 56 trans (R,R) —H —F

445 57 trans (RS,RS) —H —F

461 58 trans (RS,RS) —H —F

493 59 trans (RS,RS) —H —F

454 60 trans (R,R) —H —F

454 61 trans (RS,RS) —H —Cl

470 62 trans (R,R) —H —F

486 63 trans (RS,RS) —H —Cl

538 64 trans (RS,RS) methyl —Cl

65 trans (RS,RS) —H —H

427 66 trans (R,R) isopropyl —F

487 67 trans (RS,RS) isopropyl —Cl

530 68 trans (R,R) isopropyl —F

514 69 trans (R,R) isopropyl —F

496 70 trans (S,S) —H —F

471 71 trans (RS,RS) —H —Cl

461 72 trans (RS,RS) —H —CF₃

495 73 trans (RS,RS) —H —CF₃

522 74 trans (RS,RS) —H —CF₃

504 75 trans (R,R) —H —F

470 76 trans (RS,RS) —H —Cl

486 77 trans (R,R)

—F

548 78 trans (R,R) —H —F

486 79 trans (RS,RS) —H —Cl

502 80 trans (R,R) —H —F

499 81 trans (RS,RS) —H —Cl

515 82 trans (R,R) —H —F

493 83 trans (R,R) —H —F

507 84 trans (R,R) —H —F

488 85 trans (RS,RS) —H —F

497 86 trans (RS,RS) —H —F

481

EXAMPLE 87

(3R,4R)-4-{[4-[(Tert-butylamino)carbonyl]-4-(2-fluorophenyl)piperidin-1-yl]carbonyl}-3-(4-fluorophenyl)piperidiniumchlorideStep A: Preparation of4-(2-fluorophenyl)-1-methylpiperidine-4-carbonitrile

N-Methyl-bis-(2′-chloroethyl)amine hydrochloride (8.36 g; 43.1 mmol) wassuspended in 60 mL of methylene chloride followed by the addition of 1eq. of triethylamine (6.0 mL). After 45 min, the mixture was filtered ona medium-pore fritted Buchner funnel to remove the triethylammoniumchloride salt. The filtrate was concentrated in vacuo resulting in theprecipitation of additional salt. The filtration was repeated 2 moretimes to provide pure N-methyl-bis-(2′-chloroethyl)amine. The amine wascombined with (2-fluorophenyl)acetonitrile (8.01 g; 43.1 mmol) andtetra-n-butylammonium sulfate (1.46 g; 4.31 mmol) followed by theaddition of toluene (15 mL). To this solution was added 12.5 N sodiumhydroxide dropwise over 10 min. The reaction mixture was heated to 75°C. until the starting material had been consumed,poured into H₂O (100mL) and extracted three times with 200 mL methylene chloride. Thecombined organic extracts were washed with brine, dried (Na₂SO₄),filtered and concentrated in vacuo. The crude residue was purified onsilica gel by first elution with 50:50 ethyl acetate/hexanes followed by95:5 methylene chloride/methanol (containing 10% v/v ammonium hydroxide)to provide the titled compound

Step B: Preparation of4-carboxy-4-(2-fluorophenyl)-1-methyl-piperidinium chloride

The product of Step A (4.5 g; 20.6 mmol) was heated to 135° C. inconcentrated hydrochloric acid (25 mL). The volatiles were removed invacuo which provided the crude product. The residue was suspended intoluene (20 mL) and heated under reduced pressure to remove the toluene.This process was repeated three times which furnished the title compoundas a powder.

Step C: Preparation ofN-(tert-butyl)-4-(2-fluorophenyl)-1-methyl-piperidine-4-carboxamide

To a suspension of the product of the previous step (1.0 g; 3.63 mmol)in methylene chloride (15 mL) was added 4 drops of N,N-dimethylformamideand the mixture was cooled to 0° C. A solution of oxalyl chloride (2.0 Min methylene chloride; 1.25 eq; 2.27 mL) was added dropwise over 10 min.After an additional 30 min at 0° C., the reaction mixture was allowed towarm to ambient temperature for 2 h at which time tert-butyl amine (5eq.; 1.92 mL) was added dropwise. The resultant mixture was maintainedat room temperature for 18 h and then quenched with a saturated solutionof sodium bicarbonate. The aqueous layer was extracted three times withmethylene chloride. The combined extracts were washed with brine, dried(Na₂SO₄), filtered and concentrated in vacuo. The crude residue waspurified on silica gel and eluted with 95:5 methylene chloride/methanol(containing 10% v/v ammonium hydroxide) which provided 550 mg of thetitle compound.

Step D: Preparation ofN-(tert-butyl)-4-(2-fluorophenyl)piperidine-4-carboxamide

To a solution of the product of step C (550 mg; 1.88 mmol) in toluene(10 mL) was added 1-chloroethyl chloroformate (15 mmol; 1.62 mL) and thereaction was heated to reflux for 36 h. The volatiles were removed invacuo, the crude carbamate was then dissolved in methanol (10 mL) andthe resultant solution was heated to reflux for 2 h. The volatiles wereremoved in vacuo, the crude amine was dissolved in methylene chloride(100 mL) and the solution was washed with a saturated solution of sodiumbicarbonate, brine and the compound dried (Na₂SO₄). The drying agent wasremoved by filtration and the volatiles were removed in vacuo to furnishthe crude product which was purified on silica gel using a gradientelution (95:5 then 90:10 methylene chloride/methanol (containing 10% v/vammonium hydroxide) to afford the title compound.

Step E: Preparation of(3R,4R)-4-{[4-[(tert-butylamino)carbonyl]-4-(2-fluorophenyl)piperidin-1-yl]carbonyl}-3-(4-fluorophenyl)-piperidiniumchloride

The product of step D (70 mg) was combined with(3R,4R)-1-(tert-butoxycarbonyl)-3-(4-fluorophenyl)piperidine-4-carboxylicacid (0.1971 mmol; 55 mg), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimidehydrochloride (57 mg) and 1-hydroxybenzotriazole (40 mg) to whichmethylene chloride (2.5 mL) was added. The reaction mixture wasmaintained at ambient temperature for 24 h. The reaction mixture wasdiluted with methylene chloride (100 mL),washed with a saturatedsolution of sodium bicarbonate, brine and dried (Na₂SO₄). The dryingagent was removed by filtration and the volatiles were removed in vacuoto furnish the crude N-BOC protected product which was purified onsilica gel (eluted with 50:50 to 75:25 ethyl acetate:hexane). The N-BOCprotected product was dissolved in ethyl acetate (2 mL) and a saturatedsolution of hydrogen chloride in ethyl acetate (2 mL) was added. Thereaction mixture was maintained at ambient temperature for 90 min. Thevolatiles were removed in vacuo, the crude product was triturated twicewith diethyl ether, and the purified product was dried in vacuo toprovide 55 mg of the title compound [MS: m/z 484 (MH⁺)].

Following a procedure similar to that described above for Example 87,the following compounds were prepared:

Relative stereo. Parent Ion Ex. # (3,4) R³ X Y m/z 88 trans (RS,RS) —Fphenyl phenyl 443 89 trans (RS,RS) —F phenyl —H 367 90 trans (RS,RS) —F

—H 381 91 trans (S,S) —F

439 92 trans (S,S) —F

—CH₂CH═CH₂ 389 93 trans (S,S) —F

methyl 363 94 trans (S,S) —F

—H 349 95 trans (S,S) —F

phenyl 466 96 trans (RS,RS) —Cl

2-fluorophenyl 500 97 trans (R,R) —F

2-fluorophenyl 498 98 trans (RS,RS) —Cl

2-fluorophenyl 514 99 trans (R,R) —F

4-iodophenyl 592 100 trans (RS,RS) —Cl

4-iodophenyl 608 101 trans (R,R) —F

4-(CF₃)phenyl 534 102 trans (RS,RS) —Cl

4-(CF₃)phenyl 550 103 trans (R,R) —F

4-chlorophenyl 500 104 trans (RS,RS) —Cl

4-chlorophenyl 516 105 trans (R,R) —F

3,4-difluorophenyl 502 106 trans (RS,RS) —Cl

3,4-difluorophenyl 518 107 trans (R,R) —F

3-chlorophenyl 500 108 trans (RS,RS) —F

2,4-dichlorophenyl 548 109 trans (RS,RS) —F

3-methoxyphenyl 510

EXAMPLE 110

(3S,4R)-3-({4-Cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidin-1-yl}carbonyl)-4-(4-fluorophenyl)piperidiniumtrifluoroacetateStep A: Preparation of 3-(ethoxycarbonyl)-4-oxopiperidinium chloride

A mixture of ethyl 1-benzyl-4-oxopiderine-3-carboxylate hydrochloride(25.0 g, 84.0 mmol) and 10% Pd/C (2.5 g Degussa Type E101) inethanol/water (1:1; 300 mL) was hydrogenated at 50 psi for 4 h. Theresulting mixture was filtered through celite® and the filtrateevaporated in vacuo to give the title compound as a brown solid (84mmol).

Step B: Preparation of 1-tert-butyl 3-ethyl4-oxopiperidine-1,3-dicarboxylate

Di-tert-butyldicarbonate (21.2 g, 97.0 mmol) was added in one portion toa stirred mixture of the crude product of step A (84.0 mmol), sodiumbicarbonate (7.7 g, 92.0 mmol) and sodium chloride (14.7 g, 252 mmol) inwater/chloroform (1:2; 300 mL) and the resulting mixture heated at 60°C. for 3 h. After cooling to room temperature, the organic phase wasseparated and the aqueous phase extracted three times with chloroform.The combined organic extracts were washed with brine, dried (MgSO₄) andconcentrated in vacuo. The residue (33.8 g) was used without furtherpurification in the subsequent reaction.

Step C: Preparation of 1-tert-butyl 3-ethyl4-{[(trifluoromethyl)-sulfonyl]oxy}-5,6-dihydropyridine-1,3(2H)-dicarboxylate

Trifluoromethanesulfonic anhydride (15.5 mL, 92.0 mmol) was added overapproximately 0.1 h, via syringe, to a stirred solution of the productof step B (33.8 g, 84.0 mmol) and N,N-diisopropylethylamine (17.6 mL,101.0 mmol) in methylene chloride (300 mL) at −78° C. After allowing towarm to ambient temperature overnight, the reaction mixture was quenchedwith saturated aqueous sodium bicarbonate, poured into water andextracted three times with methylene chloride. The combined organicextracts were washed with brine, dried (MgSO₄) and concentrated invacuo. Purification of the residue by flash chromatography on silica gel(gradient elution; 0–20% ethyl acetate/hexanes as eluent) gave the titlecompound as an amber colored oil (23.0 g).

Step D: Preparation of 1-tert-butyl 3-ethyl4-(4-fluorophenyl)-5,6-dihydropyridine-1,3(2H)-dicarboxylate

A vigorously stirred suspension of the product of step C (1.00 g, 2.48mmol), 4-fluorophenylboronic acid (0.382 g, 2.73 mmol) and[1,1′-bis(diphenylphosphino)-ferrocene)dichloropalladium(II) (0.102 g,0.124 mmol) in toluene/ethanol (3:2; 24.0 mL) was degassed via threevacuum/nitrogen ingress cycles and then heated to approximately 80° C.Aqueous 2 M sodium carbonate (3.10 mL, 6.20 mmol) was added dropwise viasyringe and the resulting mixture maintained at reflux overnight. Aftercooling to ambient temperature, the reaction mixture was diluted withethyl acetate and filtered through celite®. The filtrate was poured intowater and extracted three times with ethyl acetate. The combined organicextracts were washed with brine, dried (MgSO₄) and concentrated invacuo. Purification of the residue by medium pressure liquidchromatography on silica gel (gradient elution; 0–15% ethylacetate/hexanes as eluent) afforded the title compound as a colorlessoil (0.762 g).

Step E: Preparation of 1-tert-butyl 3-ethyl4-(4-fluorophenyl)piperidine-1,3-dicarboxylate

Magnesium metal (0.525 g, 21.8 mmol) was added in three portions overapproximately 0.3 h to a stirred solution of the product of step D(0.762 g, 2.18 mmol) in methanol at ambient temperature. After stirringovernight, the reaction mixture was poured into 1 N hydrochloric acid(100 mL) and extracted three times with ethyl acetate. The combinedorganic extracts were washed with saturated sodium bicarbonate, brine,dried (MgSO₄) and concentrated in vacuo. Purification of the residue bymedium pressure liquid chromatography on silica gel (gradient elution;0–25% ethyl acetate/hexanes as eluent) furnished the title compound (3:1mixture of cis/trans diastereoisomers) as a colorless oil (0.651 g).

Step F: Preparation of(±)-trans-1-(tert-butoxycarbonyl)-4-(4-fluorophenyl)piperidine-3-carboxylicacid

Excess sodium metal was added to a stirred solution of the product ofstep E (0.651 g, 1.85 mmol) in methanol (5.0 mL) at ambient temperature,and the resulting solution was heated to 75° C. After approximately 1 h,5 M sodium hydroxide (3.0 mL) was added and the reaction mixture heatedto 100° C. for an additional 1 h. After cooling to room temperature, thereaction mixture was acidified to pH 5 with 2 N hydrochloric acid andextracted three times with methylene chloride. The combined organicextracts were washed with brine, dried (MgSO₄) and concentrated invacuo. The crude product was used without further purification in thesubsequent reaction.

Step G: Preparation of(±)-trans-3-({4-cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidin-1-yl}carbonyl)-4-(4fluorophenyl)piperidiniumtrifluoroacetate

1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (0.0174 g,0.091 mmol) was added to a stirred mixture of the crude product of stepF (0.0294 g, 0.091 mmol),4-cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidiniumchloride (0.025 g, 0.076 mmol), 1-hydroxybenzotriazole (0.0123 g, 0.091mmol) and N-methylmorpholine (0.010 mL, 0.091 mmol) in methylenechloride (0.500 mL) at ambient temperature. After approximately 18 h,the reaction mixture was poured into water/saturated sodium bicarbonate(1:1) and extracted three times with methylene chloride. The combinedorganic extracts were washed with brine, dried (Na₂SO₄) and concentratedin vacuo. A saturated solution of hydrogen chloride in ethyl acetate(1.0 mL) was added to a solution of the crude amide in methylenechloride (1.0 mL) at room temperature. After 18 h, the volatiles wereevaporated in vacuo, and the crude residue purified by preparativereversed phase high pressure liquid chromatography on YMC Pack Pro C18phase (gradient elution; 0–100% acetonitrile/water as eluent, 0.1% TFAas modifier) to give the title compound (0.031 g) as an off-white solid[MS: m/z 500 (MH⁺)].

Following a procedure similar to that described above for Example 110,the following compounds can be prepared:

Relative stereo. Parent Ion Ex. # (3,4) R¹ R² m/z 111 trans (RS,RS) —H3-chlorophenyl 516 112 trans (RS,RS) —H 4-methoxyphenyl 512 113 trans(RS,RS) —H 4-chlorophenyl 516 114 trans (R,R) methyl 4-fluorophenyl 115trans (R,R) methyl 3-chlorophenyl 116 trans (R,R) methyl 4-methoxyphenyl117 trans (R,R) methyl 4-chlorophenyl 118 trans (R,R) isopropyl4-fluorophenyl 119 trans (R,R) isopropyl 4-chlorophenyl 120 trans (R,R)isopropyl 2,4-difluorophenyl

EXAMPLE 121

(3S,4R)-3-({4-Cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidin-1-yl}carbonyl)-4-(4-fluorophenyl)-1-isopropylpyrrolidiniumchlorideStep A: Preparation of(4S)-4-benzyl-3-[(2E)-3-(4-fluorophenyl)prop-2-enoyl]-1,3-oxazolidin-2-one

A flame-dried 1 L 3-necked flask equipped with a mechanical stirrer wascharged with (2E)-3-(4-fluorophenyl)prop-2-enoic acid (20.769 g; 0.125mol) and tetrahydrofuran (275 mL). The reaction was cooled to −20° C.followed by the sequential addition of triethylamine (16.443 g; 0.163mol) and trimethylacetyl chloride (16.580 g; 0.138 mol). After 30 min,the reaction was warmed to ambient temperature where it remained for anadditional 90 min. A separate 2 L 3-necked flask, equipped with amechanical stirrer, and a filter funnel, was charged with(S)-4-benzyloxazolidinone (20.20 g; 0.114 mol), anhydrous powderedlithium chloride (5.316 g; 0.125 mol), tetrahydrofuran (500 mL) andtriethylamine (14.996 g; 0.148 mol) and cooled to −20° C. The mixedanhydride was rapidly added to the oxazolidinone solution through thefilter funnel using a slight vacuum. After 30 min, the reaction wasallowed to warm to ambient temperature for 5 h. The reaction wasfiltered through a fritted-funnel and concentrated in vacuo. The cruderesidue was diluted with ethyl acetate, washed with 1 N hydrochloricacid, saturated sodium bicarbonate, brine, dried (MgSO₄), filtered andconcentrated in vacuo. The crude product was purified on a silica gelchromatography column eluted with methylene chloride. Evaporation of thepurified fractions and drying in vacuo afforded 26.36 g of the titlecompound.

Step B: Preparation of(4S)-4-benzyl-3-{[(3R,4R)-1-benzyl-4-(4fluorophenyl)pyrrolidin-3-yl]carbonyl}-1,3-oxazolidin-2-one

To a cooled (0° C.) solution of the product of step A (12.667 g; 38.9mmol) in methylene chloride (110 mL) was addedN-(methoxymethyl)-N-(trimethylsilylmethyl)benzylamine (13.866 g; 58.4mmol) followed by a catalytic amount of trifluoroacetic acid (0.15 mL).After 10 min at 0° C., the reaction was allowed to warm to ambienttemperature for 8 h. The reaction mixture was diluted with methylenechloride and washed with saturated saturated sodium bicarbonate, brine,dried (MgSO₄), filtered and concentrated in vacuo. The crude residue waspurified on a silica gel chromatography column eluted with methylenechloride to afford 7.42 g of the less polar diastereoisomer and 7.79 gof the more polar diastereoisomer.

Step C: Preparation of tert-butyl(3R,4R)-3-{[(4S)-4-benzyl-2-oxo-1,3-oxazolidin-3-yl]carbonyl}-4-(4-fluorophenyl)pyrrolidine-1-carboxylate

To a suspension of the product of step B (2.0 g; 4.4 mmol) in toluene(20 mL) was added 4 eq of 1-chloroethyl chloroformate (17.5 mmol; 1.33mL). The reaction was heated to 100° C. for 6 h at which time startingmaterial still remained. Thus, an additional 2 eq. of 1-chloroethylchloroformate (8.8 mmol; 0.66 mL) was added and heating was resumed foranother 20 h. The volatiles were removed in vacuo and the crudecarbamate was dissolved in methanol (20 mL). The reaction mixture washeated to 70° C. for 2 h. The volatiles were removed in vacuo and thecrude amine was dissolved in methylene chloride (400 mL) followed bywashing the organic solution with saturated sodium bicarbonate andbrine. The organic phase was dried (Na₂SO₄), filtered and concentratedin vacuo to provide the crude amine which was purified on silica gelusing a gradient elution (50% ethyl acetate/hexane to elute the startingmaterial followed by 9:1 methylene chloride/methanol (containing 10% v/vammonium hydroxide). This provided 720 mg of the desired amine. Theamine (720 mg; 1.96 mmol) was dissolved in methylene chloride (5 mL) andsaturated sodium bicarbonate (5 mL) was added followed bydi-tert-butyldicarbonate (533 mg; 2.45 mmol). After 1 h, the mixture wasdiluted with methylene chloride (100 mL) followed by washing the organicsolution with saturated sodium bicarbonate and brine. The organic phasewas dried (Na₂SO₄), filtered and concentrated in vacuo. The crudeproduct was purified on silica gel (30% ethyl acetate/hexane) whichfurnished 840 mg of the title compound.

Step D: Preparation of(3R,4R)-1-(tert-butoxycarbonyl)-4-(4-fluorophenyl)pyrrolidine-3-carboxylicacid

To a cooled (0° C.) solution of the product of step C (835 mg; 1.78mmol) lithium hydroxide (85 mg; 3.56 mmol) in 15 mL of a 4:1 mixture oftetrahydrofuran-water was added a 30% aqueous solution of hydrogenperoxide. After 5 min, the solution was warmed to ambient temperatureand stirred for 5 h. The reaction mixture was poured into a 10% aqueoussolution of sodium sulfite and then acidified to pH 3 with 1 Nhydrochloric acid. The aqueous solution was extracted three times withethyl acetate. The organic phase was washed with brine, dried (MgSO₄),filtered, concentrated in vacuo and the crude acid was purified onsilica gel (30% ethyl acetate/hexane with 1% acetic acid) whichfurnished 520 mg of the title compound.

Step E: Preparation of(3R,4R)-3-({4-cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3oxazolidin-3-yl)methyl]piperidin-1-yl}carbonyl)-4-(4-fluorophenyl)pyrrolidiniumchloride

To a suspension of4-cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidiniumchloride (150 mg; 0.4532 mmol) in methylene chloride (4.0 mL) was addedN-methylmorpholine (183 mg; 0.2 mL). After 20 min, the followingreagents were added sequentially:1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (130 mg;0.6798 mmol), 1-hydroxybenzotriazole (92 mg; 0.6798 mmol) and theproduct of step D (154 mg; 0.4985 mmol). The final reaction mixture wasmaintained at ambient temperature for 48 h. The reaction mixture wasdiluted with methylene chloride (100 mL) followed by washing the organicsolution with saturated sodium bicarbonate and brine. The organic phasewas dried (Na₂SO₄), filtered and concentrated in vacuo to provide thecrude N-BOC protected pyrrolidine that was purified on silica gel (50%ethyl acetate/hexane as the elution solvent). The crude N-BOC protectedpyrrolidine was then dissolved in ethyl acetate (2 mL) followed by theaddition of a saturated solution of hydrogen chloride in ethyl acetate(2 mL). The reaction mixture was maintained at ambient temperature for 2h at which time the volatiles were removed in vacuo. The crude productwas triturated to high purity with diethyl ether which furnished 204 mgof the title compound as a hydrochloride salt.

Step F: Preparation of(3S,4R)-3-({4-cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidin-1-yl}carbonyl)-4-(4-fluorophenyl)-1-isopropylpyrrolidiniumchloride

A solution of the product of step E (100 mg; 0.1916 mmol) in methylenechloride (100 mL) was converted to the free-base by washing withsaturated sodium bicarbonate. The organic phase was washed with brine,dried (Na₂SO₄), filtered and the volatiles were removed in vacuo. Theresidue was dissolved in methylene chloride (2 mL) and cooled to 0° C.Acetone (111 mg; 0.14 mmol) was added, followed by acetic acid (57 mg;0.9579 mmol) and sodium triacetoxyborohydride (0.575 mmol). The reactionmixture was stirred and allowed to warm to room temperature over 36 h atwhich time the reaction was quenched with saturated sodium bicarbonate.After extracting three times with methylene chloride, the organicsolution was washed with brine, dried (Na₂SO₄), filtered andconcentrated in vacuo to provide the crude residue which was purified onsilica gel (93:7 methylene chloride/methanol (contaiing 10% v/v ammoniumhydroxide). The product was dissolved in ethyl acetate (2 mL) andconverted to the hydrochloride salt by addition of a saturated solutionof hydrogen chloride in ethyl acetate (2 mL). The reaction mixture wasmaintained at ambient temperature for 30 min at which time the volatileswere removed in vacuo. The solid was triturated to high purity withdiethyl ether which furnished 95 mg of the title compound as thehydrochloride salt [MS: m/z 528 (MH⁺)].

Following a procedure similar to that described above for Example 121the following compounds were prepared:

Ex. Relative stereo. Parent Ion # (3,4) R¹ R² m/z 122 trans (SR,RS)

4-chlorophenyl 592 123 trans (SR,RS) —H 4-chlorophenyl 502 124 trans(R,S) —H 4-chlorophenyl 502 125 trans (R,S) methyl 4-chlorophenyl 516126 trans (R,S) isopropyl 4-chlorophenyl 544 127 trans (S,R) —H4-chlorophenyl 502 128 trans (S,R) methyl 4-chlorophenyl 516 129 trans(S,R) isopropyl 4-chlorophenyl 544 130 trans (SR,RS) —H 4-fluorophenyl486 131 trans (SR,RS) isopropyl 4-fluorophenyl 528 132 trans (SR,RS)ethyl 4-fluorophenyl 514 133 trans (SR,RS) —H 3,4- 536 dichlorophenyl134 trans (SR,RS) isopropyl 3,4- 578 dichlorophenyl 135 trans (S,R) —H4-fluorophenyl 486 136 trans (S,R) ethyl 4-fluorophenyl 514 137 trans(S,R)

4-fluorophenyl 564 138 trans (SR,RS) —H 3,4- 504 difluorophenyl 139trans (SR,RS) isopropyl 3,4- 546 difluorophenyl 140 trans (SR,RS) —H2,4- 504 difluorophenyl 141 trans (SR,RS) isopropyl 2,4- 546difluorophenyl 142 trans (S,R) —H 2,4- 504 difluorophenyl 143 trans(S,R) isopropyl 2,4- 546 difluorophenyl 144 trans (S,R) ethyl 2,4- 532difluorophenyl 145 trans (S,R) —CH₂C(CH₃)₃ 2,4- 574 difluorophenyl 146trans (SR,RS) —H 3-chloro-4- 520 fluorophenyl 147 trans (SR,RS)isopropyl 3-chloro-4- 562 fluorophenyl 148 trans (SR,RS) —H 3,4- 503difluorophenyl 149 trans (SR,RS) isopropyl 3,4- 546 difluorophenyl 150trans (SR,RS) —H 2-thiophene 474 151 trans (SR,RS) isopropyl 2-thiophene516 152 trans (SR,RS) —H 2-(3-chloro- 508 thiophene) 153 trans (SR,RS)isopropyl 2-(3-chloro- 550 thiophene)

EXAMPLE 154

(±)-trans-1-Tert-butyl-3-({4-cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidin-1-yl}carbonyl)-4-(4-fluorophenyl)pyrrolidiniumtrifluoroacetateStep A: Preparation of N-tert-butyl-N-(trimethylsilylmethyl)amine

A mixture of tert-butylamine (18.0 mL, 171 mmol) and(chloromethyl)trimethylsilane (7.00 g, 57.1 mmol) was heated in athick-walled glass tube at 200° C. overnight. After cooling to ambienttemperature, the reaction mixture was poured into 1 N sodium hydroxideand extracted three times with diethyl ether. The combined organicextracts were washed with brine, dried (MgSO₄), and the volatilesevaporated in vacuo. Distillation (atmospheric pressure; ˜135° C.) ofthe residual liquid gave the title compound as a colorless liquid (7.67g).

Step B: Preparation ofN-tert-butyl-N-(methoxymethyl)-N-(trimethylsilylmethyl)amine

N-tert-Butyl-N-(trimethylsilylmethyl)amine (8.47 g, 53.1 mmol) was addeddropwise, over approximately 30 min, via a pressure equalizing additionfunnel to a stirred solution of aqueous formaldehyde (5.98 mL of a 37wt. % solution in water, 79.7 mmol) at 0° C. (ice cooling). After 45min, methanol (6.45 mL, 159.3 mmol) was added and the resulting solutionwas saturated with potassium carbonate. After stirring vigorously forapproximately 5 h, the aqueous phase was removed. The organic phase wassaturated with potassium carbonate and stirred overnight. The reactionmixture was poured into water and extracted three times with diethylether. The combined organic extracts were washed with brine, dried(MgSO₄) and the volatiles evaporated in vacuo. Distillation (highvacuum; ˜70° C.) of the residual liquid afforded the title compound as acolorless liquid (3.50 g).

Step C: Preparation of methyl(±)-trans-1-tert-butyl-4-(4-fluorophenyl)-pyrrolidine-3-carboxylate

Trifluoroacetic acid (38.9 mL, 0.505 mmol) was added to a solution ofthe product of step B (1.03 g, 5.05 mmol) and methyl(2E)-3-(4-fluorophenyl)prop-2-enoate (1.00 g, 5.05 mmol) in methylenechloride (10 mL) at ambient temperature. After 18 h, the reactionmixture was poured into saturated aqueous sodium bicarbonate andextracted three times with methylene chloride. The combined organicextracts were washed with brine, dried (Na₂SO₄) and concentrated invacuo. Purification of the crude residue by medium pressure liquidchromatography on silica gel (gradient elution; 0–9% methanol(containing 10% v/v ammonium hydroxide)/methylene chloride as eluent)furnished the title compound as a colorless liquid (1.06 g).

Step D: Preparation of(±)-trans-1-tert-butyl-3-carboxy-4-(4-fluorophenyl)pyrrolidiniumchloride

A solution of the product of Step C (50.0 mg, 0.179 mmol) in 8 Nhydrochloric acid (1.0 mL) was heated at reflux overnight. After coolingto room temperature, the volatiles were evaporated and the residualsolid used without further purification in the subsequent reaction.

Step E: Preparation of(±)-trans-1-tert-butyl-3-({4-cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidin-1-yl}carbonyl)-4-(4-fluorophenyl)pyrrolidiniumtrifluoroacetate

1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (51.5 mg,0.269 mmol) was added to a stirred mixture of4-cyclohexyl4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidiniumchloride (54.9 mg, 0.166 mmol), crude product of step D (0.179 mmol),1-hydroxybenzotriazole (36.3 mg, 0.269 mmol) and N-methylmorpholine(59.0 L, 0.537 mmol) in methylene chloride (1.8 mL) at ambienttemperature. After approximately 18 h, the reaction mixture was pouredinto saturated aqueous sodium bicarbonate and extracted three times withmethylene chloride. The combined organic extracts were washed withbrine, dried (Na₂SO₄) and concentrated in vacuo. Purification of theresidue by preparative reversed phase high pressure liquidchromatography on YMC Pack Pro C18 phase (gradient elution; 0–100%acetonitrile/water as eluent, 0.1% TFA as modifier) gave the titlecompound as an off-white solid [MS: m/z 542 (MH⁺)].

Following a procedure similar to that described above for Example 154,the following compounds were prepared:

Relative stereo. Parent Ion Ex. # (3,4) X R² m/z 155 trans (S,R)

2,4-difluorophenyl 560 156 trans (R.S)

2,4-difluorophenyl 560 157 trans (SR,RS)

2,3,4-trifluorophenyl 578 158 trans (SR,RS)

2-chloro-4-fluorophenyl 576 150 trans (SR,RS)

2-iodo-4-fluoro-6-chlorophenyl 686 160 trans (SR,RS)

2,5-difluorophenyl 574 161 trans (SR,RS)

2,4-difluorophenyl 505 162 trans (SR,RS)

4-fluorophenyl 487 163 trans (S,R)

2,4-difluorophenyl 532 164 trans (R,S)

2,4-difluorophenyl 532 165 trans (SR,RS)

2,4-difluorophenyl 532 166 trans (SR,RS)

4-fluorophenyl 514 167 trans (S,R)

2,4-difluorophenyl 519 168 trans (R,S)

2,4-difluorophenyl 519 169 trans (S,R)

2,4-difluorophenyl 546 170 trans (S,R)

2,4-difluorophenyl 572 171 trans (S,R)

2,4-difluorophenyl 560 172 trans (S,R)

2,4-difluorophenyl 584 173 trans (S,R)

2,4-difluorophenyl 544 174 trans (S,R)

2,4-difluorophenyl 532 175 trans (S,R)

2,4-difluorophenyl 546 176 trans (S,R)

2,4-difluorophenyl 532 177 trans (S,R)

2,4-difluorophenyl 530 178 trans (S,R)

2,4-difluorophenyl 546 179 trans (S,R)

2,4-difluorophenyl 516 180 trans (S,R)

2,4-difluorophenyl 516 181 trans (S,R)

2,4-difluorophenyl 572 182 trans (S,R)

2,4-difluorophenyl 521 183 trans (S,R)

2,4-difluorophenyl 537 184 trans (S,R)

2,4-difluorophenyl 553 185 trans (S,R)

2,4-difluorophenyl 493 186 trans (S,R)

2,4-difluorophenyl 509 187 trans (S,R)

2,4-difluorophenyl 525 188 trans (S,R)

2,4-difluorophenyl 507 189 trans (S,R)

2,4-difluorophenyl 523 190 trans (S,R)

2,4-difluorophenyl 539 191 trans (S,R)

2,4-difluorophenyl 521 192 trans (S,R)

2,4-difluorophenyl 537 193 trans (S,R)

2,4-difluorophenyl 553 194 trans (S,R)

2,4-difluorophenyl 549 195 trans (S,R)

2,4-difluorophenyl 565 196 trans (S,R)

2,4-difluorophenyl 565 197 trans (S,R)

2,4-difluorophenyl 542 198 trans (S,R)

2,4-difluorophenyl 544 199 trans (S,R)

2,4-difluorophenyl 516 200 trans (S,R)

2,4-difluorophenyl 530 201 trans (S,R)

2,4-difluorophenyl 558

EXAMPLE 202

(±)-trans-1-Tert-butyl4-({4-cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidin-1-yl}carbonyl)-3-(2,4-difluorophenyl)piperidiniumchlorideStep A: Preparation of ethyl 4-(ten-butylamino)butanoate

Ethyl 4-bromobutyrate (20 g; 102.6 mmol) was combined withtert-butylamine (37.2 g; 0.514 mol) and heated to 100° C. in a sealedtube for 24 h. The contents of the reaction were cooled to ambienttemperature, the volatiles were removed in vacuo and the crude productwas dissolved in 1 N hydrochloric acid. The aqueous layer was extractedtwice with diethyl ether and the organic layer discarded. The aqueouslayer was adjusted to pH 9 with 2.5 N sodium hydroxide. The aqueouslayer was extracted three times with diethyl ether. The combined organicextracts (from the pH 9 aqueous layer) were washed with brine, dried(Na₂SO₄), filtered and the solvent was removed in vacuo to afford thetitle compound (14.2 g).

Step B: Preparation of ethylN-(tert-butyl)-N-(2-ethoxy-2-oxoethyl)4-aminobutanoate

To a solution of the product of step A (14.2 g; 75.5 mmol) in toluene(150 mL) was added potassium carbonate (20.8 g; 151.1 mmol) and ethylbromoacetate (18.9 g; 113.3 mmol). The reaction was heated to 120° C.for 24 h. The reaction mixture was cooled to ambient temperature andpartitioned between 1 N hydrochloric acid and diethyl ether. The aqueouslayer was extracted twice with diethyl ether and the organic layerdiscarded. The aqueous layer was adjusted to pH 9 with 2.5 N sodiumhydroxide and extracted three times with diethyl ether. The combinedorganic extracts (from the pH 9 aqueous layer) were washed with brine,dried (Na₂SO₄), filtered and concentrated in vacuo to furnish the titlecompound (19.2 g).

Step C: Preparation of ethyl 1-tert-butyl-3-oxopiperidine-4-carboxylate

To a solution of the product of step B (14.0 g; 50.9 mmol) intetrahydrofuran (200 mL) was added 1.05 eq of potassium tert-butoxide(6.0 g; 53.5 mmol). The reaction was maintained at ambient temperaturefor 2 h and then quenched with a sufficient amount of saturated aqueousammonium chloride to make the solution pH 8. The tetrahydrofuran wasremoved in vacuo and the aqueous layer was extracted three times withdiethyl ether. The combined organic extracts were washed with brine,dried (Na₂SO₄), filtered and concentrated in vacuo to afford the titlecompound (7.15 g).

Step D: Preparation of ethyl1-tert-butyl-5-{[(trifluoromethyl)sulfonyl]-oxy}-1,2,3,6-tetrahydropyridine-4-carboxylate

To a cooled (−78° C.) solution of the product of step C (7.15 g; 31.2mmol) in methylene chloride (100 mL) was added diisopropylethylamine(5.04 g; 39.0 mmol). Triflic anhydride (9.69 g; 34.3 mmol) was thenadded dropwise over 10 min and the reaction mixture was allowed to warmto ambient temperature over 16 h. The mixture was concentrated to about50% of the initial volume and directly loaded onto silica gel elutedwith 50% ethyl acetate/hexane. Evaporation of the purified fractionsprovided 5.05 g of the title compound.

Step E: Preparation of ethyl1-tert-butyl-5-(2,4-difluorophenyl)-1,2,3,6-tetrahydropyridine-4-carboxylate

The product of step D (5.05 g; 14.4 mmol), 2,4-difluorophenylboronicacid (2.85 g; 18.0 mmol) and[1,1′-bis(diphenylphosphino)ferrocene)dichloropalladium(II) (0.589 g;0.7 mmol) were combined and dissolved a 2:1 mixture of toluene:ethanol(54 mL). The reaction was heated to 80° C. followed by the dropwiseaddition of 2 M aqueous sodium carbonate over 10 min. The reaction wasmaintained at 80° C. for 2 h. The reaction was quenched with saturatedaqueous sodium bicarbonate and the aqueous layer was extracted threetimes with ethyl acetate. The combined organic extracts were washed withbrine, dried (Na₂SO₄), filtered concentrated in vacuo. The crude residuewas purified on silica gel using a gradient elution (30%→40%→60% ethylacetate/hexane) which furnished the title compound (2.8 g).

Step F: Preparation of methyl(±)-trans-1-tert-butyl-3-(2,4-difluorophenyl)piperidine-4-carboxylate

The product of step E (1 g; 3.1 mmol) was dissolved in ethanol (20 mL)and treated with acetic acid (280 mg; 4.6 mmol) and 20% palladiumhydroxide on carbon catalyst (0.760 g). The reaction mixture was stirredfor 24 h under 1 atmosphere of hydrogen gas. The reaction was filteredthrough celite® and the filter cake was rinsed with copious amounts ofmethanol. The solvents were evaporated and the crude residue wasdissolved in methylene chloride. The organic solution was washed withsaturated sodium bicarbonate, brine, dried (Na₂SO₄), filtered andconcentrated in vacuo. The crude residue was purified on silica gelusing 10% methanol/methylene chloride to provide predominantly thecis-disubstituted piperidine. The cis isomer, accumulated from severalexperiments as described above, (5.5 g; 17.0 mmol) was dissolved inmethanol (75 mL) followed by the addition of freshly cut sodium metal(1.27 g; 55.3 mmol). The reaction mixture was heated to 70° C. for 12 h.The reaction was quenched with saturated aqueous ammonium chloride andthe aqueous layer was extracted with ethyl acetate. The combined organicextracts were dried (Na₂SO₄), filtered and concentrated in vacuo. Thecrude residue was purified on silica gel (50% ethyl acetate/hexane)which furnished the title compound.

Step G: Preparation of(±)-trans-1-tert-butyl-4-carboxy-3-(2,4-difluorophenyl)piperidiniumchloride

The product of step F (160 mg; 0.515 mmol) was heated to 100° C. inconcentrated hydrochloric acid for 16 h. The volatiles were removed invacuo and the crude residue was suspended in toluene and evaporated todryness. This process was repeated three times to provide 170 mg of thetitle compound.

Step H: Preparation of(±)-trans-1-tert-butyl-4-({4-cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidin-1-yl}carbonyl)-3-(2,4-difluorophenyl)piperidiniumchloride

To a suspension of4-cyclohexyl-4-[(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]piperidiniumchloride (45 mg; 0.136 mmol) in methylene chloride (2.0 mL) was addedN-methylmorpholine (35 mg; 0.036 mL). A separate flask was charged withthe product of step G (50 mg; 0.1497 mmol), methylene chloride (2.0 mL),and N-methylmorpholine (35 mg; 0.036 mL) was added. After 20 min, thefollowing reagents were added sequentially to the flask containing theproduct of step G: 1-(3-dimethylaminopropyl)-3-ethylcarbodiimidehydrochloride (39 mg; 0.204 mmol), 1-hydroxybenzotriazole (28 mg; 0.204mmol) followed by the dropwise addition of the piperidine solution fromthe first flask. The final reaction mixture was maintained at ambienttemperature for 48 h. The reaction was diluted with methylene chloride(100 mL) then washed with saturated sodium bicarbonate and brine. Themixture was dried (Na₂SO₄), filtered and concentrated in vacuo toprovide a crude product that was purified on silica gel (eluted firstwith 75% ethyl acetate/hexane followed by 95:5 methylenechloride/methanol (containing10% v/v ammonium hydroxide)). The purifiedproduct was dissolved in ethyl acetate (2 mL) and converted to thehydrochloride salt by treatment with a saturated solution of hydroogenchloride in ethyl acetate (2 mL). The reaction mixture was maintained atambient temperature for 1 h at which time the volatiles were removed invacuo. The crude hydrochloride salt was triturated to high purity withdiethyl ether which furnished 50 mg of the title compound [MS: m/z 574(MH⁺)].

Following a procedure similar to that described above for Example 202,the following compounds can be prepared:

Relative stereo. Parent Ion Ex. # (3,4) X R² m/z 203 trans (S,S)

2,4-difluorophenyl 575 204 trans (R,R)

2,4-difluorophenyl 575 205 trans (S,S)

2,4-difluorophenyl 206 trans (R,R)

2,4-difluorophenyl 207 trans (S,S)

2-fluorophenyl 208 trans (S,S)

2-fluorophenyl 209 trans (S,S)

2,4-difluorophenyl 547 210 trans (R,R)

2,4-difluorophenyl 547 211 trans (R,R)

2-fluorophenyl 212 trans (R,R)

2-fluorophenyl 213 trans (R,R)

2,4-difluorophenyl 563

EXAMPLE 214

(±)-3-{[4-Cyclohexyl-4-(ethoxycarbonyl)piperidin-1-yl]carbonyl}-2-phenylpyrrolidiniumtrifluoroacetateStep A: Preparation of ethyl(±)-1-{[1-(tert-butoxycarbonyl)-2-phenylpyrrolidin-3-yl]carbonyl}-4-cyclohexylpiperidine4-carboxylate

1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (1.09 mL ofa 0.25 M solution in methylene chloride, 0.272 mmol) was added to astirred mixture of 4-cyclohexyl-4-(ethoxycarbonyl)piperidinium chloride(50.0 mg, 0.181 mmol),(±)-1-(tert-butoxycarbonyl)-2-phenylpyrrolidine-3-carboxylic acid (68.6mg, 0.235 mmol), 1-hydroxybenzotriazole (36.7 mg, 0.272 mmol) andN-methylmorpholine (59.7 μL, 0.543 mmol) in methylene chloride (0.7 mL)at ambient temperature. After approximately 18 h, the reaction mixturewas poured into saturated aqueous sodium bicarbonate and extracted threetimes with methylene chloride. The combined organic extracts were washedwith brine, dried (Na₂SO₄) and concentrated in vacuo. The crude residuewas used without further purification in the subsequent reaction.

Step B: Preparation of(±)-3-{[4-cyclohexyl-4-(ethoxycarbonyl)piperidin-1-yl]carbonyl}-2-phenylprrolidiniumchloride

A saturated solution of hydrogen chloride in ethyl acetate (2.0 mL) wasadded to a solution of the crude product of step A in methylene chloride(1.0 mL) at room temperature. After 18 h, the volatiles were evaporatedin vacuo, and the crude residue purified by preparative reversed phasehigh pressure liquid chromatography on YMC Pack Pro C18 phase (gradientelution; 0–100% acetonitrile/water as eluent, 0.1% TFA as modifier) togive the title compound (59.1 mg) as an off-white solid [MS: m/z 413(MH⁺)].

Following a procedure similar to that described above for Example 214,the following compounds were prepared:

Parent Ion Ex. # X R m/z 215

413 216

427 217

427 218

431 219

449 220

443 221

537 222

473 223

459 224

440 225

482 226

474

Biological Assays

A. Binding Assay. The membrane binding assay was used to identifycompetitive inhibitors of ¹²⁵I-NDP-alpha-MSH binding to cloned humanMCRs expressed in mouse L- or Chinese hamster ovary (CHO)-cells.

Cell lines expressing melanocortin receptors were grown in T-180 flaskscontaining selective medium of the composition: 1 L Dulbecco's modifiedEagles Medium (DMEM) with 4.5 g L-glucose, 25 mM Hepes, without sodiumpyruvate, (Gibco/BRl); 100 ml 10% heat-inactivated fetal bovine serum(Sigma); 10 mL 10,000 unit/mL penicillin & 10,000 μg/mL streptomycin(Gibco/BRl); 10 ml 200 mM L-glutamine (Gibco/BRl); 1 mg/mL geneticin(G418) (Gibco/BRl). The cells were grown at 37° C. with CO₂ and humiditycontrol until the desired cell density and cell number was obtained.

The medium was poured off and 10 mls/monolayer of enzyme-freedissociation media (Specialty Media Inc.) was added. The cells wereincubated at 37° C. for 10 min or until cells sloughed off when flaskwas banged against hand.

The cells were harvested into 200 mL centrifuge tubes and spun at 1000rpm, 4° C., for 10 min. The supernatant was discarded and the cells wereresuspended in 5 mls/monolayer membrane preparation buffer having thecomposition: 10 mM Tris pH 7.2–7.4; 4 μg/mL Leupeptin (Sigma); 10 μMPhosphoramidon (Boehringer Mannheim); 40 μg/mL Bacitracin (Sigma); 5μg/mL Aprotinin (Sigma); 10 mM Pefabloc (Boehringer Mannheim). The cellswere homogenized with motor-driven dounce (Talboy setting 40), using 10strokes and the homogenate centrifuged at 6,000 rpm, 4° C., for 15 min.

The pellets were resuspended in 0.2 mls/monolayer membrane prep bufferand aliquots were placed in tubes (500–1000 μL/tube) and quick frozen inliquid nitrogen and then stored at −80° C.

Test compounds or unlabelled NDP-α-MSH was added to 100 μL of membranebinding buffer to a final concentration of 1 μM. The membrane bindingbuffer had the composition: 50 mM Tris pH 7.2; 2 mM CaCl₂; 1 mM MgCl₂; 5mM KCl; 0.2% BSA; 4 μg/mL Leupeptin (SIGMA); 10 μM Phosphoramidon(Boehringer Mannheim); 40 μg/mL Bacitracin (SIGMA); 5 μg/mL Aprotinin(SIGMA); and 10 mM Pefabloc (Boehringer Mannheim). One hundred μL ofmembrane binding buffer containing 10–40 μg membrane protein was added,followed by 100 μM 125I-NDP-α-MSH to final concentration of 100 pM. Theresulting mixture was vortexed briefly and incubated for 90–120 min atroom temp while shaking.

The mixture was filtered with Packard Microplate 196 filter apparatususing Packard Unifilter 96-well GF/C filter with 0.1% polyethyleneimine(Sigma). The filter was washed (5 times with a total of 10 mL per well)with room temperature of filter wash having the composition: 50 mMTris-HCl pH 7.2 and 20 mM NaCl. The filter was dried, and the bottomsealed and 50 μL of Packard Microscint-20 was added to each well. Thetop was sealed and the radioactivity quantitated in a Packard TopcountMicroplate Scintillation counter.

B. Functional Assay

Functional cell based assays were developed to discriminate melanocortinreceptor agonists from antagonists.

Cells (for example, CHO— or L-cells or other eukaryotic cells)expressing a human melanocortin receptor (see e.g. Yang-Y K; Ollmann-MM; Wilson-B D; Dickinson-C; Yamada-T; Barsh-G S; Gantz-I;Mol-Endocrinol. 1997 Mar; 11(3): 274–80) were dissociated from tissueculture flasks by rinsing with Ca and Mg free phosphate buffered saline(14190-136, Life Technologies, Gaithersburg, Md.) and detached following5 min incubation at 37° C. with enzyme free dissociation buffer(S-014-B, Specialty Media, Lavellette, N.J.). Cells were collected bycentrifugation and resuspended in Earle's Balanced Salt Solution(14015-069, Life Technologies, Gaithersburg, Md.) with additions of 10mM HEPES pH 7.5, 5 mM MgCl₂, 1 mM glutamine and 1 mg/ml bovine serumalbumin. Cells were counted and diluted to 1 to 5×10⁶/mL. Thephosphodiesterase inhibitor 3-isobutyl-1-methylxanthine was added tocells to 0.6 mM.

Test compounds were diluted in dimethylsulfoxide (DMSO) (10⁻⁵ to 10⁻¹⁰M) and 0.1 volume of compound solution was added to 0.9 volumes of cellsuspension; the final DMSO concentration was 1%. After room temperatureincubation for 45 min, cells were lysed by incubation at 100° C. for 5min to release accumulated cAMP.

cAMP was measured in an aliquot of the cell lysate with the Amersham(Arlington Heights, Ill.) cAMP detection assay (RPA556). The amount ofcAMP production which resulted from an unknown compound was compared tothat amount of cAMP produced in response to alpha-MSH which was definedas a 100% agonist. The EC₅₀ is defined as the compound concentrationwhich results in half maximal stimulation, when compared to its ownmaximal level of stimulation.

Antagonist assay: Antagonist activity was defined as the ability of acompound to block cAMP production in response to alpha-MSH. Solution oftest compounds and suspension of receptor containing cells were preparedand mixed as described above; the mixture was incubated for 15 min, andan EC50 dose (approximately 10 nM alpha-MSH) was added to the cells. Theassay was terminated at 45 min and cAMP quantitated as above. Percentinhibition was determined by comparing the amount of cAMP produced inthe presence to that produced in the absence of test compound.

C. In Vivo Food Intake Models

1) Overnight food intake. Sprague Dawley rats are injectedintracerebroventricularly with a test compound in 400 nL of 50%propylene glycol/artificial cerebrospinal fluid one hour prior to onsetof dark cycle (12 hours). Food intake is determined using a computerizedsystem in which each rat's food is placed on a computer monitoredbalance. Cumulative food intake for 16 h post compound administration ismeasured.

2) Food intake in diet induced obese mice. Male C57/B16J mice maintainedon a high fat diet (60% fat calories) for 6.5 months from 4 weeks of ageare are dosed intraperitoneally with test compound. Food intake and bodyweight are measured over an eight day period. Biochemical parametersrelating to obesity, including leptin, insulin, triglyceride, free fattyacid, cholesterol and serum glucose levels are determined.

D. Rat Ex Copula Assay

Sexually mature male Caesarian Derived Sprague Dawley (CD) rats (over 60days old) are used with the suspensory ligament surgically removed toprevent retraction of the penis back into the penile sheath during theex copula evaluations. Animals receive food and water ad lib and arekept on a normal light/dark cycle. Studies are conducted during thelight cycle.

1) Conditioning to Supine Restraint for Ex Copula Reflex Tests. Thisconditioning takes ˜4 days. Day 1, the animals are placed in a darkenedrestrainer and left for 15–30 minutes. Day 2, the animals are restrainedin a supine position in the restrainer for 15–30 minutes. Day 3, theanimals are restrained in the supine position with the penile sheathretracted for 15–30 minutes. Day 4, the animals are restrained in thesupine position with the penile sheath retracted until penile responsesare observed. Some animals require additional days of conditioningbefore they are completely acclimated to the procedures; non-respondersare removed from further evaluation. After any handling or evaluationanimals are given a treat to ensure positive reinforcement.

2) Ex Copula Reflex Tests. Rats are gently restrained in a supineposition with their anterior torso placed inside a cylinder of adequatesize to allow for normal head and paw grooming. For a 400–500 gram rat,the diameter of the cylinder is approximately 8 cm. The lower torso andhind limbs are restrained with a non-adhesive material (vetrap). Anadditional piece of vetrap with a hole in it, through which the glanspenis will be passed, is fastened over the animal to maintain thepreputial sheath in a retracted position. Penile responses will beobserved, typically termed ex copula genital reflex tests. Typically, aseries of penile erections will occur spontaneously within a few minutesafter sheath retraction. The types of normal reflexogenic erectileresponses include elongation, engorgement, cup and flip. An elongationis classified as an extension of the penile body. Engorgement is adilation of the glans penis. A cup is defined as an intense erectionwhere the distal margin of the glans penis momentarily flares open toform a cup. A flip is a dorsiflexion of the penile body.

Baseline and or vehicle evaluations are conducted to determine how andif an animal will respond. Some animals have a long duration until thefirst response while others are non-responders altogether. During thisbaseline evaluation latency to first response, number and type ofresponses are recorded. The testing time frame is 15 minutes after thefirst response.

After a minimum of 1 day between evaluations, these same animals areadministered the test compound at 20 mg/kg and evaluated for penilereflexes. All evaluations are videotaped and scored later. Data arecollected and analyzed using paired 2 tailed t-tests to comparedbaseline and/or vehicle evaluations to drug treated evaluations forindividual animals. Groups of a minimum of 4 animals are utilized toreduce variability.

Positive reference controls are included in each study to assure thevalidity of the study. Animals can be dosed by a number of routes ofadministration depending on the nature of the study to be performed. Theroutes of administration includes intravenous (IV), intraperitoneal(IP), subcutaneous (SC) and intracerebral ventricular (ICV).

E. Models of Female Sexual Dysfunction

Rodent assays relevant to female sexual receptivity include thebehavioral model of lordosis and direct observations of copulatoryactivity. There is also a urethrogenital reflex model in anesthetizedspinally transected rats for measuring orgasm in both male and femalerats. These and other established animal models of female sexualdysfunction are described in McKenna K E et al, A Model For The Study ofSexual Function In Anesthetized Male And Female Rats, Am. J. Physiol.(Regulatory Integrative Comp. Physiol 30): R1276–R1285, 1991; McKenna KE et al, Modulation By Peripheral Serotonin of The Threshold For SexualReflexes In Female Rats, Pharm. Bioch. Behav., 40:151–156, 1991; andTakahashi L K et al, Dual Estradiol Action In The Diencephalon And TheRegulation Of Sociosexual Behavior In Female Golden Hamsters, BrainRes., 359:194–207, 1985.

Representative compounds of the present invention were tested and foundto bind to the melanocortin-4 receptor. These compounds were generallyfound to have IC₅₀ values less than 2 μM. Representative compounds ofthe present invention were also tested in the functional assay and foundgenerally to activate the melanocortin-4 receptor with EC₅₀ values lessthan 1 μM.

Examples of a Pharmaceutical Composition

As a specific embodiment of an oral composition of a composition of thepresent invention, 5 mg of Example 169 is formulated with sufficientfinely divided lactose to provide a total amount of 580 to 590 mg tofill a size O hard gelatin capsule.

As another specific embodiment of an oral composition of a compound ofthe present invention, 10 mg of Example 174 is formulated withsufficient finely divided lactose to provide a total amount of 580 to590 mg to fill a size O hard gelatin capsule.

While the invention has been described and illustrated in reference tocertain preferred embodiments thereof, those skilled in the art willappreciate that various changes, modifications and substitutions can bemade therein without departing from the spirit and scope of theinvention. For example, effective dosages other than the preferred dosesas set forth hereinabove may be applicable as a consequence ofvariations in the responsiveness of the mammal being treated forseverity of bone disorders caused by resorption, or for otherindications for the compounds of the invention indicated above.Likewise, the specific pharmacological responses observed may varyaccording to and depending upon the particular active compound selectedor whether there are present pharmaceutical carriers, as well as thetype of formulation and mode of administration employed, and suchexpected variations or differences in the results are contemplated inaccordance with the objects and practices of the present invention. Itis intended, therefore, that the invention be limited only by the scopeof the claims which follow and that such claims be interpreted asbroadly as is reasonable.

1. A compound of structural formula I:

or a pharmaceutically acceptable salt thereof; wherein r is 1 or 2; s is 1; n is 0, 1 or 2; p is 0, 1, or 2; R¹ is selected from the group consisting of hydrogen, amidino, C₁₋₄ alkyliminoyl, C₁₋₁₀ alkyl, (CH₂)_(n)-C₃₋₇ cycloalkyl, (CH₂)_(n)-phenyl, (CH₂)_(n)-naphthyl, and (CH₂)_(n)-heteroaryl wherein heteroaryl is selected from the group consisting of (1) pyridinyl, (2) furyl, (3) thienyl, (4) pyrrolyl, (5) oxazolyl, (6) thiazolyl, (7) imidazolyl, (8) pyrazolyl, (9) isoxazolyl, (10) isothiazolyl, (11) pyrimidinyl, (12) pyrazinyl, (13) pyridazinyl, (14) quinolyl, (15) isoquinolyl, (16) benzimidazolyl, (17) benzofuryl, (18) benzothienyl, (19) indolyl, (20) benzthiazolyl, and (21) benzoxazolyl; in which phenyl, naphthyl, and heteroaryl are unsubstituted or substituted with one to three groups independently selected from R³; and alkyl and cycloalkyl are unsubstituted or substituted with one to three groups independently selected from R³ and oxo; R² is selected from the group consisting of phenyl, naphthyl, and heteroaryl wherein heteroaryl is selected from the group consisting of (1) pyridinyl, (2) furyl, (3) thienyl, (4) pyrrolyl, (5) oxazolyl, (6) thiazolyl, (7) imidazolyl, (8) pyrazolyl, (9) isoxazolyl, (10) isothiazolyl, (11) pyrimidinyl, (12) pyrazinyl, (13) pyridazinyl, (14) quinolyl, (15) isoquinolyl, (16) benzimidazolyl, (17) benzofuryl, (18) benzothienyl, (19) indolyl, (20) benzthiazolyl, and (21) benzoxazolyl; in which phenyl, naphthyl, and heteroaryl are unsubstituted or substituted with one to three groups independently selected from R³; R³ is selected from the group consisting of C₁₋₆ alkyl, (CH₂)_(n)-phenyl, (CH₂)_(n)-naphthyl, (CH₂)_(n)-heteroaryl, (CH₂)_(n)-heterocyclyl, (CH₂)_(n)C₃₋₇ cycloalkyl, halogen, OR⁴, (CH₂)_(n)N(R⁴)₂, (CH₂)_(n)C≡N, CO₂R⁴, C(R⁴)(R⁴)N(R⁴)₂, NO₂, (CH₂)_(n)NR⁴SO₂R⁴ (CH₂)_(n)SO₂N(R⁴)₂, (CH₂)_(n)S(O)_(p)R⁴, (CH₂)_(n)NR⁴C(O)N(R⁴)₂, (CH₂)_(n)C(O)N(R⁴)₂, (CH₂)_(n)NR⁴C(O)R⁴, (CH₂)_(n)NR⁴CO₂R⁴, CF₃, CH₂CF₃, OCF₃, and OCH₂CF₃; in which heteroaryl is as defined above; phenyl, naphthyl, heteroaryl, cycloalkyl, and heterocyclyl are unsubstituted or substituted with one to three substituents independently selected from halogen, hydroxy, C₁₋₄ alkyl, trifluoromethyl, and C₁₋₄ alkoxy; and (CH₂)_(n) is unsubstituted or substituted with one to two groups independently selected from halogen, hydroxy, and C₁₋₄ alkyl; each R⁴ is independently selected from the group consisting of hydrogen, C₁₋₆ alkyl, (CH₂)_(n)-phenyl, (CH₂)_(n)-naphthyl, and (CH₂)_(n)C₃₋₇ cycloalkyl; wherein cycloalkyl is unsubstituted or substituted with one to three groups independently selected from halogen, C₁₋₄ alkyl, and C₁₋₄ alkoxy; or two R⁴ groups together with the atom to which they are attached form a 4- to 8-membered mono- or bicyclic ring system optionally containing an additional heteroatom selected from O, S, and NC₁₋₄ alkyl; each R⁵ is independently selected from the group consisting of hydrogen, C₁₋₈ alkyl, (CH₂)_(n)-phenyl, (CH₂)_(n)-naphthyl, (CH₂)_(n)-heteroaryl, and (CH₂)_(n)C₃₋₇ cycloalkyl; wherein heteroaryl is as defined above; phenyl, naphthyl, and heteroaryl are unsubstituted or substituted with one to three groups independently selected from R³; and alkyl, cycloalkyl, and (CH₂)_(n) are unsubstituted or substituted with one to three groups independently selected from R³ and oxo; or two R⁵ groups together with the atom to which they are attached form a 5- to 8-membered mono- or bicyclic ring system optionally containing an additional heteroatom selected from O, S, and NC₁₋₄ alkyl; X is C₁₋₈ alkyl, unsubstituted or substituted with one to three groups independently selected from OR⁴; (CH₂)_(n)CON(R⁵R⁵), (CH₂)_(n)CO₂R⁵, and (CH₂)_(n)N(R⁵)(R⁵), wherein alkyl, and (CH₂)_(n), are unsubstituted or substituted with one to three groups independently selected from R³ and oxo; and Y is cyclohexyl, wherein cyclohexyl is optionally substituted with one to three groups independently selected from R³ and oxo.
 2. The compound of claim 1 wherein R¹ is selected from the group consisting of hydrogen, C₁₋₆ alkyl, (CH₂)₀₋₁C₃₋₆ cycloalkyl, and (CH₂)₀₋₁-phenyl; wherein phenyl is unsubstituted or substituted with one to three groups independently selected from R³; and alkyl and cycloalkyl are optionally substituted with one to three groups independently selected from R³ and oxo.
 3. The compound of claim 1 wherein R² is phenyl or thienyl optionally substituted with one to three groups independently selected from R³.
 4. The compound of claim 3 wherein R² is phenyl optionally substituted with one to three groups independently selected from R³.
 5. The compound of claim 1 wherein X is selected from the group consisting of C₁₋₆ alkyl, unsubstituted or substituted with one to three groups independently selected from OR⁴; (CH₂)₀₋₁CO₂R⁵, and (CH₂)₀₋₁C(O)N(R⁵)(R⁵); wherein alkyl is optionally substituted with one to three groups independently selected from R³ and oxo.
 6. The compound of claim 1 of structural formula IIa or IIb of the indicated trans relative stereochemical configuration:

or a pharmaceutically acceptable salt thereof; wherein r is 1 or 2; n is 0, 1, or 2; p is 0, 1, or 2; R¹ is hydrogen, amidino, C₁₋₄ alkyliminoyl, C₁₋₆ alkyl, C₅₋₆ cycloalkyl, (CH₂)₀₋₁ phenyl, or (CH₂)₀₋₁ heteroaryl; wherein phenyl and heteroaryl are unsubstituted or substituted with one to three groups independently selected from R³; and alkyl and cycloalkyl are unsubstituted or substituted with one to three groups independently selected from R³ and oxo; R² is phenyl or thienyl optionally substituted with one to three groups independently selected from R³; R³ is selected from the group consisting of C₁₋₆ alkyl, (CH₂)_(n)-phenyl, (CH₂)_(n)-naphthyl, (CH₂)_(n)-heteroaryl, (CH₂)_(n)-heterocyclyl, (CH₂)_(n)C₃₋₇ cycloalkyl, halogen, OR⁴, (CH₂)_(n)N(R⁴)₂, (CH₂)_(n)C≡N, CO₂R⁴, C(R⁴)(R⁴)N(R⁴)₂, NO₂, (CH₂)_(n)NR⁴SO₂R⁴ (CH₂)_(n)SO₂N(R⁴)₂, (CH₂)_(n)S(O)_(p)R⁴, (CH₂)_(n)NR⁴C(O)N(R⁴)₂, (CH₂)_(n)C(O)N(R⁴)₂, (CH₂)_(n)NR⁴C(O)R⁴, (CH₂)_(n)NR⁴CO₂R⁴, CF₃, CH₂CF₃, OCF₃, and OCH₂CF₃; in which phenyl, naphthyl, heteroaryl, cycloalkyl, and heterocyclyl are unsubstituted or substituted with one to two substituents independently selected from halogen, hydroxy, C₁₋₄ alkyl, trifluoromethyl, and C₁₋₄ alkoxy; and (CH₂)_(n) is unsubstituted or substituted with one to two groups independently selected from halogen, hydroxy, and C₁₋₄ alkyl; each R⁴ is independently selected from the group consisting of hydrogen, C₁₋₈ alkyl, and C₃₋₆ cycloalkyl; wherein cycloalkyl is unsubstituted or substituted with one to three groups independently selected from halogen, C₁₋₄ alkyl, and C₁₋₄ alkoxy; or two R⁴ groups together with the atom to which they are attached form a 4- to 8-membered mono- or bicyclic ring system optionally containing an additional heteroatom selected from O, S, and NC₁₋₄ alkyl; Y is cyclohexyl, wherein cyclohexyl is unsubstituted or substituted with one to three groups independently selected from R³ and oxo; and X is selected from the group consisting of


7. The compound of claim 1 of structural formula IIIa or IIIb of the indicated trans relative stereochemical configuration:

or a pharmaceutically acceptable salt thereof; wherein r is 1 or 2; R¹ is hydrogen, C₁₋₄ alkyl, or (CH₂)₀₋₁ phenyl; each R³ is independently selected from the group consisting of hydrogen, halo, C₁₋₄ alkyl, trifluoromethyl, and C₁₋₄ alkoxy; Y is cyclohexyl; and X is selected from the group consisting of


8. The compound of claim 7 selected from the group consisting of:

or a pharmaceutically acceptable salt thereof.
 9. A pharmaceutical composition which comprises a therapeutically effective amount of a compound of claim 1 and a pharmaceutically acceptable carrier.
 10. A method for the treatment of obesity in a subject in need thereof which comprises administering to the subject a therapeutically effective amount of a compound according to claim
 1. 11. A method for the treatment of diabetes mellitus in a subject in need thereof comprising administering to the subject a therapeutically effective amount of a compound according to claim
 1. 12. A method for the treatment of erectile dysfunction in a subject in need thereof comprising administering to the subject a therapeutically effective amount of a compound according to claim
 1. 